ABORATORY  AND 
ELD  EXERCISES 

DENSMORE 


QK53 


I 


THIS   BOOK  CARD 


I- 


University  Research  Library 


;  • 


This  book  is  DUE  on  the  last  date  stamped  below 


&    MAR    7 
MAR    7197^ 


Form  L-9-5m-5.'24 


LABORATORY  AND  FIELD 
EXERCISES 

FOR  "GENERAL  BOTANY" 


BY 

HIRAM  D.  DENSMORE 

I'KOFESSOK  OF   BOTANY   AT   BELOIT   COLLEGE 


GINN  AND  COMPANY 

?W  YORK    •    CHICA 
LAS    •    COLUMBUS 

51167 


BOSTON    •     NEW  YORK    •    CHICAGO    •    LONDON 
ATLANTA    •    DALLAS    •    COLUMBUS    •    SAN   FRANCISCO 


COPYRIGHT,  1920,  BY 
HIRAM  D.  DENSMORE 


ALL    RIGHTS    RESERVED 
320.6 


<Cbt   atftenatum   &rte* 

GINN  AND  COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


PREFACE 

These  laboratory  and  field  exercises  have  been  written  to 
accompany  the  author's  textbook  in  general  botany,  and  the 
topics  for  the  practical  exercises  are  therefore  arranged  in  the 
same  order  as  in  the  text. 

;*         Both  the  textbook  and  the  exercises  have  been  used  with 

^     several  generations  of  students  and  instructors,  whose  criticisms 

and  suggestion's  are  embodied  in  this  revision  of  the  field  and 

laboratory  exercises  for  publication.    The  topics  in  the  practical 

exercises  also  follow  those  of  the  text  and  are  divided  into 

^    three  more  or  less  distinct  parts. 

Part  I  contains  directions  for  some  field  work,  laboratory 
work,  and  experiments  on  the  general  form,  structure,  and 
physiology  of  the  higher  green  plants. 

Part  II  is  devoted  to  practical  laboratory  exercises  relating 

*  to  the  general  morphology  and  relationship  of  the  great  plant 
K   groups,  from  the  algse  and  fungi  to  the  highest  seed  plants. 

^    The  laboratory  exercises  on  anatomy  in  Part  II  are  designed  to 

•  enable  teachers  not  familiar  with  the  methods  of  the  new  anat- 
omy to  direct  students  in  the  study  of  plant  structure  from  the 
more  modern  standpoint.    It  is  hoped  that  the  diagrams  and 
discussions  of  the  text  on  anatomy  will  materially  assist  both 
teachers  and  students  in  making  the  exercises  clear. 

Part  III  contains  directions  for  field  work  on  trees,  shrubs, 
and  herbaceous  plants,  considered  from  a  general  ecological 
standpoint.  A  brief  study  of  plant  associations  has  been  added, 
in  order  to  introduce  the  student  to  the  study  of  plants  in  their 
social  relations.  Emphasis  is  also  laid,  in  the  exercises  as  in 

iii 


iv  .LABORATORY  AND  FIELD  EXERCISES 

the  textbook,  on  the  study  of  plants  as  living  organisms,  closely 
related  and  adapted  to  the  environment  at  all  seasons  of  the 
year.  The  few  species  selected  for  field  study  are  taken  from 
families  represented  in  the  spring  flora  which  are  of  special 
biological  or  economic  interest.  No  attempt  has  been  made  to 
outline  practical  studies  for  all  important  families  of  the  spring 
flora,  since  only  a  limited  number  of  species  could  be  studied 
in  an  introductory  course  in  college  botany. 

Although  these  exercises  have  been  written  to  accompany 
the  author's  textbook,  they  can  easily  be  adapted  for  use  with 
any  text,  or  to  accompany  lectures  in  an  introductory  course 
in  botany  or  plant  biology. 


CONTENTS 


PART  I.  BIOLOGY  OF  THE  HIGHER  SEED  PLANTS 
SECTION  I.   PLANTS  AND  THE  ENVIRONMENT 

PAGE 

A.  THE  BODY  PLAN  AXD  FORM  OF  PLANTS 3 

The  Lilac 3 

Herbaceous  Plants 6 

Trees  (Spruces  and  Pines) 9 

Trees  (the  American  Elm) 13 

B.  ADJUSTMENT  TO  THE  ENVIRONMENT 18 

The  Embryo  and  Seedling  of  the  Bean        18 

Experiments 20 

Supplementary  Studies 21 

SECTION  II.    CELL  STRUCTURE  AND  GROWTH 

A.  THE  CELLULAR  STRUCTURE  OF  PLANTS .22 

Cell-Wall  Thickening  and  Cell  Differentiation 24 

Protoplasm,  Vacuoles,  and  Nuclei  in  Root-Tip  Cells     ...  26 
Cell  Structure  and  Protoplasmic  Streaming  in  Stamen  Hairs 

of  Tradexcantia t .27 

Plastids  in  Plant  Cells 30 

B.  CELL  STRUCTURE  AND  GROWTH 31 

Growth 31 

C.  THE  CELL  AND  CELL  DIVISION       35 

Supplementary  Studies 39 


vi  LABORATORY  AND  FIELD  EXERCISES 

SECTION  III.    ANATOMY 

PAGE 

A.  ANATOMY  OF  STEMS 41 

External  Features  of  Woody  Stems 41 

Gross  Structure  of  Mature  Stems 42 

Microscopic  Structure  of  Woody  Stems 45 

Herbaceous  Stems  (Dicotyledons) 50 

Herbaceous  Stems  (Monocotyledons) 52 

B.  STRUCTURE  OF  ROOTS 53 

C.  THE  STRUCTURE  OF  THE  LEAF 53 

SECTION  IV.    PHYSIOLOGY  OF  PLANTS 

A.  PHOTOSYNTHESIS 57 

B.  RESPIRATION 60 

C.  TRANSPIRATION  AND  WATER  ASCENT 61 

SECTION  V.    REPRODUCTION 

A.  SEXUAL  REPRODUCTION 64 

The  Flower  and  its  Parts 64 

Pollination  in  Papilionaceous  Flowers 68 

Structure  of  Papilionaceous  Flowers 69 

PART  II.    THE  PLANT  GROUPS 
SECTION  VI.   THALLOPHYTES  (ALGJG  AND  FUNGI) 

A.  THE  ALG.E 75 

Protococcus  (Pfatrocoeciu) 75 

Chlamydomonas 76 

Spirogyra t  77 

Vaucheria 79 

(Edogonium 81 

General  Study  of  Fresh-Water  Algae 82 

Fucus  vesiculosus     .                                                        ...  83 


CONTENTS  vii 

PAGE 

B.  THE  FUNGI 86 

Yeast 86 

Bacteria • 89 

Molds .'•.  92 

Mushrooms  and  their  Allies 97 

Mushrooms  and  their  Allies  (Rusts  and  Smuts)      ....  100 

Lichens 101 

Lilac  Mildew 102 

SECTION  VII.    BRYOPHYTA  (LIVERWORTS  AND  MOSSES) 

A.  HEPATIC^  (LIVER WORTS) 103 

B.  Musci  (MoBSKs) 108 

SECTION  VIII.    PTERIDOPHYTA  (FERNS,  EQUISETA, 
AND  LYCOPODS) 

.1.  FILICALES  (TRUE  FERNS) 113 

B.  EQUISETALES  (HORSETAILS) 123 

C.  L  YCOPODIALES  (CLUB    MOSSES)       . 126 

Lycopodium 126 

Selaginella 127 

SECTION  IX.    GYMNOSPERMS 

A.  CYCADALES  (CYCADS) 130 

B.  CONIFERALES  (SPRUCES    AND    PlNES) 135 

SECTION  X.  ANGIOSPERMS  (DICOTYLEDONS) 

Sporophyte 143 

Capsella  (Shepherd's  Purse) 149 

PART  III.   THE  SPRING  FLORA 

SECTION  XI.   FIELD  WORK  (DICOTYLEDONS) 

A.  TREES  AND  SHRUBS 155 

A  Method  of  recording  Field  Observations    ......  155 


viii          LABORATORY  AND  FIELD  EXERCISES 

PAGE 

Gymnosperms  (Softwood  Trees) 159 

Angiosperms  (Hardwood  Trees) 161 

B.  HERBACEOUS  DICOTYLEDONS 107 

A  Method  of  recording  Field  Observations 167 

Ranunculaceae 171 

Violaceae 173 

Cruciferae 175 

Leguminosae 177 

Rosaceae 179 

Compositae 181 

SECTION  XII.    FIELD  WORK  (MONOCOTYLEDONS) 

A.  TRADESCANTIA,  TULIP,  AND  OTHER  MONOCOTYLEDONS  .     .  185 

B.  SOLOMON'S  SEAL  (POLYGOXATUM  AND  SMILACINA)    .     .     .  188 

C.  IRIDACEAE  AND    ARACEAE 190 

D.  GRAMINEAE 191 

SECTION  XIII.   PLANT  ASSOCIATIONS 

Nature  and  Composition  of  Plant  Associations 192 

Kinds  of  Associations 194 

Origin  of  New  Associations 195 

INDEX     .                                                                                                        .  197 


LABORATORY  AND  FIELD  EXERCISES 
FOR  "GENERAL  BOTANY" 

PART  I.    BIOLOGY  OF  THE  HIGHER 
SEED  PLANTS 


SECTION  I.   PLANTS  AND  THE 
ENVIRONMENT 

A.   THE  BODY  PLAN  AND  FORM  OF  PLANTS 
THE  LILAC 

1.  Leaves.    Do  the  leaves  spring  from  definite  points  on  the 

axis  of  the  main  stem  and  its  branches,  or  are  they 
irregularly  arranged?  Are  they  cyclic  (two  or  more 
leaves  attached  at  the  same  level)  or  spiral  in  arrange- 
ment ?  Are  the  leaves  so  placed  as  to  give  the  maximum 
light  to  each  leaf  ?  Observe  the  shoot  from  above.  How 
many  rows  of  leaves  are  there  along  the  stem  ?  Be  able 
to  explain  the  light  relations  of  the  leaves.  Consult 
Figs.  5  and  6  of  the  text.1 

2.  Buds  and  branches.  How  are  the  buds  related  to  the  leaves 

as  regards*  position  and  arrangement  on  the  stem  and 
branches  ?  Is  there  a  terminal  bud  in  the  lilac  ?  Do 
the  branches  have  the  same  orderly  arrangement  as  the 
buds  and  leaves  ?  "Why  ?  Do  branches  grow  from  buds  ? 

3.  Stem  divisions.    Is  the  stem  divided  into  regular  divisions 

by  the  origin  of  leaves,  buds,  and  branches  from  definite 
points  ?  Consult  the  text  under  The  Form  and  Plan  of 
the  Plant  Body  concerning  the  nature  and  relation  of 
nodes  and  internodes. 

a.  Sketch  an  entire  shoot  of  a  lilac  in  outline  to  show  the 
orderly  plan  upon  which  it  is  constructed.  Eemove 
the  leaves  on  the  side  of  the  branch  facing  you  and 

1  All  text  references  are  to  Densmore's  "General  Botany." 
3 


LABORATORY  AND  FIELD  EXERCISES 


.Terminal  bud 

3 Subliminal  latwal  bud 


indicate  their  position  by  drawing  the  scars  left  by 
their  removal.  Note  the  bud  above  the  scar,  formerly 
in  the  axil  of 
the  leaf. 

I.  Read  text  on  The 
Form  and  Plan 
of  the  Plant 
Body.  Label  all 
the  parts  of  the 
finished  draw- 
ing correctly. 
Name  the  buds 
on  the  basis  of 
position,  that 
is,  terminal  or 
lateral.  Con- 
sult Figs.  38 
and  45  of  text. 
4.  The  structure  and 

growth  of  buds, 
a.  Plan  of  the  bud. 
Observe  the  ex- 
ternal   surface 
of  the  largest 
buds    on    your          FIG.  1.  Parts  of  a  shoot  with  a  spiral 
specimen.  Use  body  plan 

hand    lens    for     The  diagram  represents  a  single  year's  growth 
of  a  woody  shoot.    The  bud-scale  scars  mark 
details.      Have  the  lower  limit  of  the  year's  growth 

the  parts  of  the 

bud  a  definite  arrangement  ?  Is  this  arrangement  the 
same  as  that  of  leaves  on  the  main  stem  ?  Separate 
the  parts  of  the  bud  carefully  and  observe  their 
origin  and  arrangement.  Is  there  a  central  axis  to 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


which  the  parts  are  attached  ?  This  point  can  be 
demonstrated  by  bisecting  the  bud.  See  Fig.  2,  and 
Fig.  37  (p.  68)  of  the  text. 

b.  Sketch  the  external  surface  of  a  bud  and  label  its  parts. 

c.  G-rowth  of  buds.    Do  all  of  the  buds  in  the  axils  of  the 

leaves  grow  each  season  ?  Ex- 
amine older  portions  of  the 
branch  to  determine  this  point. 
Are  the  branches  produced  each 
season  of  the  same  length  and 
vigor  ?  Note  the  forked  branch- 
ing due  to  the  growth  of  the 
two  vigorous  subterminal  lat- 
eral buds.  Can  you  determine 
the  age  of  the  branch  you  are 
studying  ?  Look  for  the  scars  left 
by  the  bud  scales  each  season 
(Fig.  1,  and  Fig.  38  of  the  text). 

5.  The  shrubby  form  of  the  lilac.  Study 

the  form  of  the  branch  with  which 
you  are  working,  as  well  as  that 
of  lilac  shrubs  in  the  field.  Is  the 
rounded,  shrubby  habit  of  the  lilac 
due  to  the  arrangement  and  method 
of  bud  growth  ?  For  example,  sup- 
pose the  lilac  shoots  had  a  single 
continuous  terminal  bud  instead  of  the  two  subterminal 
ones.  Would  this  change  the  form  and  habit  of  the  plant  ? 

6.  Summary  of  observations.    Answer  the  following  ques- 

tions in  the  form  of  a  summary  on  your  laboratory  sheets : 

a.  What  relation  exists  between  the  position  and  arrange- 

ment of  leaves,  buds,  and  branches  in  the  lilac  ? 

b.  What  is  meant  by  the  body  plan  of  the  plant  body  ? 


FIG.  2.  Vertical  section 
of  a  hawthorn  bud 

br  and  o,  outer  and  inner 
bud  scales;  i,  ilt  outer 
and  inner  leaves ;  g, 
growing  point,  or  meri- 
stem,  of  the  bud.  From 
Bergen  and  Caldwell's 
"Practical  Botany" 


LABORATORY  AND  FIELD  EXERCISES 


c.  What  relation  have  the  position  and  growth  of  buds  to 
the  form  of  the  lilac  shrub  ?  Illustrate  this  point  by 
means  of  an  outline  sketch. 

HERBACEOUS  PLAXTS 

Use  the  catnip,  ragweed,  aster,  or  similar  herbaceous  plants 
for  this  study. 

1.  The  main  axis.    What  is  the  form  of  the  entire  central 

axis  of  the  plant,  including  both  stem  and  root  ?  Is  this 
central  axis  me- 
chanically adapted 
to  the  support  of 
the  lateral  roots, 
branches,  and  leaves  ? 
Be  able  to  explain 
to  an  instructor.  Is 
the  main  axis  of  the 
stem  the  same  in 
shape  as  that  of  the 
root  ?  Is  the  entire 
axis  divided  into 
nodes  and  biter- 
nodes  ?  Are  the  in- 
tern odes  of  the 
same  length  in  all 
parts  of  the  axis  ? 

2.  Lateral  members.  Are 

the  leaves  cyclic  or 
spiral  in  arrange- 
ment ?  How  many 
of  the  lateral  buds 
have  produced  branches  ?  Have  these  lateral  branches 
the  same  plan  and  leaf  arrangement  as  the  main 


FIG.  3.    Cyclic  body  plan  and  leaf  dis- 
play of  the  milkweed  (Asclepias) 

Note  that  the  cyclic  leaf  arrangement 
secures  the  maximum  light  exposure.  Pho- 
tograph by  Jesse  L.  Smith.  From  Bergen 
and  Caldwell's  "Introduction  to  Botany  " 


BIOLOGY  OF  HIGHER  SEED  PLANTS  7 

axis  ?  Have  the  lateral  roots  the  same  arrangement 
as  the  leaves  and  branches  ?  Have  they  any  definite 
arrangement  ? 

3.  Bud  structure,  arrangement,  and  growth. 

a.  Structure.    How  do  the  buds  of  an  herbaceous  plant, 

like  the  catnip,  ragweed,  or  aster,  differ  from  those  of 
a  woody  plant  like  the  lilac  ?  Can  you  give  reasons 
for  the  differences  observed,  based  upon  the  annual 
and  perennial  habits  of  the  two  plants  ? 

b.  Arrangement  and  growth.    Compare   the  buds   of  the 

herbaceous  plant  examined  with  those  of  the  lilac  as 
regards  arrangement  and  mode  of  growth.  Is  the  form 
of  the  plant  you  are  examining  determined  by  the 
differences  in  the  time  and  rate  of  growth  of  the  ter- 
minal and  lateral  buds  ?  For  example,  why  are  the 
upper  branches  shorter  than  the  lower  ?  Why  is  the 
main  axis  longer  than  any  of  the  branches  ?  How 
explain  the  conical  or  rounded  form  of  herbaceous 
plants  011  the  basis  of  bud  growth? 

4.  Light,  air,  and  soil  relations.    What  is  the  form  of  the 

entire  plant  under  examination  ?  Are  the  leaves,  flowers, 
and  seeds  effectively  displayed  to  sunlight  and  to  air 
currents  ?  Are  the  tips  of  the  lateral  absorbing  roots 
properly  placed  for  absorbing  water  and  soil  salts  ? 
Consult  Figs.  8  and  9  of  the  text. 

a.  Construct  an  accurate  outline  drawing  of  the  plant  you 
are  studying,  indicating  the  following  points : 

(1)  The  form  of  the  main  central  axis  and  the  arrange- 

ment of  lateral  members. 

(2)  The  plan  of  the  lateral  branches,  including  the  posi- 

tion of  leaves,  flowers,  and  fruits  if  present. 

(3)  The  general  form  of  the  entire  plant  and  the  display 

of  absorbing  leaf  and  root  surfaces. 


PLANT  BODY 


INCOttE 


OUTGO 


l  ENERGY 


b  Liquid 


c  Solids  in     i 
•  Solution} 


FIG.  4.  Diagram  illustrating  the  general  nature  of  the  income  and  outgo 
of  a  green  plant  from  the  forces  and  materials  of  its  environment 

The  student  is  expected  to  fill  in  the  details  under  the  captions  Energy,  Gases 

Liquids,  and  Solids  (consult  Chapter  I  in  the  text).   Do  not  fill  in  a  detail  unless 

it  is  correct  to  do  so.   The  diagram  is  merely  suggestive 


BIOLOGY  OF  HIGHER  SEED  PLANTS  9 

THE  RELATION  OF  THE  CATNIP,  EAGWEED,  OR  ASTER  TO 
THE  ENVIRONMENT 

1.  Read  Chapter  I  of  the  text  carefully.    Indicate  in  connec- 

tion with  a  diagram  of  a  catnip,  ragweed,  or  aster  the 
income  and  outgo  of  the  plant  as  outlined  in  Fig.  4 
of  these  exercises. 

2.  Summarize  in  your  notes  the  essential  differences  between 

the  income  and  outgo  of  the  plant  sketched  and  that  of 
a  man.  Consult  Figs.  2  and  3  of  the  text  and  the 
accompanying  discussion  in  Chapter  I. 

TREES 
SPRUCES  AND  PINES 

1.  Form  and  general  arrangement  of  parts. 

a.  Are  the  pines  and  spruces  of  the  erect  or  of  the  spreading 

type  ?  Compare  them  with  oaks,  maples,  and  similar 
trees.  What  determines  the  fact  that  the  pine  has 
a  continuous  excurrent  trunk  ?  What  determines 
the  uniform  gradation  in  the  length  of  the  branches 
from  the  apex  to  the  base  of  the  tree  ?  Do  the 
branches  appear  to  have  any  regular  arrangement  on 
the  trunk  ?  Eecall  your  work  on  the  growth  of  buds 
and  branches  in  the  lilac. 

b.  Are  the  leaves  properly  disposed  over   the  crown   to 

secure  the  maximum  amount  of  sunlight  ?  Does  the 
form  and  the  angle  of  divergence  of  the  upper  and 
lower  branches  from  the  tree  trunk  contribute  to  the 
exposure  of  the  leaves  to  light  ?  Are  the  cones  and 
seeds  favorably  situated  for  seed  dispersal? 

c.  Sketch  the  spruce  or  pine  tree  examined,  in  a  manner 

similar  to  that  outlined  for  the  lilac  and  the  herb. 


10  LABORATORY  AND  FIELD  EXERCISES 

Draw  a  few  branches  with  leaves  on  the  upper, 
middle,  and  lower  portions  of  the  trunk.  Indicate 
the  position  of  the  remaining  branches  by  circles  or 


frogeotropic 
taproot 


Dingeotropic  roots 


FIG.  5.   Pine  trees  illustrating  the  erect  type 

a,  a  young  pine  ;  6,  a  mature  pine.  Observe  the  excurrent  trunk,  the  false  whorls 
of  branches,  and  the  pyramidal  form.   Consult  the  text  for  the  main  factors  con- 
cerned in  the  seasonal  growth  (1-7)  and  the  development  of  these  external  features 
of  the  pine 


other  symbols.  Consult  Fig.  5  above  and  the  text 
discussion  on  the  form  and  development  of  the  pine. 
d.  Summarize  briefly  the  facts  relating  to  bud  and  branch 
growth  which  determine  the  erect  pyramidal  form 
of  the  pines  and  spruces. 


BIOLOGY  OF  HIGHEK  SEED  PLANTS  11 

2.  The  plan  and  development  of  the  branches.  Select  the 
terminal  portion  of  a  branch  of  a  spruce  or  pine  rep- 
resenting three  or  four  years  of  growth  in  length. 
The  spruce  is  best  for  this  study,  but  a  pine  branch 
may  be  used. 

a.  The  parts  and  their  arrangement. 

(1)  Are  the  leaves  cyclic  or  spiral  in  their  arrange- 
ment ?  This  is  most  easily  determined  on  naked 
portions  of  the  twigs  by  means  of  the  leaf  scars. 
What  is  the  number  and  position  of  the  buds? 
Is  there  a  bud  in  the  axil  of  each  leaf,  as  in  the 
lilac  ?  Are  the  branches  disposed  like  the  buds  on 
the  main  axis?  Are  the  smaller  twigs  arranged 
like  the  main  branches  ?  Is  the  relation  between 
leaves,  buds,  and  branches  the  same  as  in  the 
lilac  and  the  herbaceous  plant  studied  ? 

b.  Seasonal  growth  of  buds  and  branches. 

(1)  Determine   the  limits  of   each  season's  growth  in 

length  on  the  main  axis  and  the  lateral  branches. 
Is  there  a  uniform  number  of  buds  which  grow 
each  season  to  continue  the  central  axis  and  to 
produce  lateral  branches  ?  Are  some  branches 
more  vigorous  than  others  ?  Do  the  vigorous 
lateral  branches  produce  twigg  and  buds  disposed 
like  those  on  the  main  central  axis  of  the  branch  ? 
Observe  old  branches  of  pine  and  spruce.  What 
becomes  of  the  lateral  branches  produced  each 
season  ?  Do  the  leaves  persist  on  the  main  axis 
between  the  annual  branches  ?  The  clusters  of 
lateral  annual  branches  in  the  pine  and  spruce 
are  called  false  whorh  of  branches. 

(2)  Sketch  the  entire  branch  examined  above,  to  illus- 

trate the  points  outlined  under  a  and  b.  Illustrate 


12  LABORATORY  AND  FIELD  EXERCISES 

the  arrangement  of  the  leaves  on  a  small  portion 
of  a  single  twig.    Label  all  parts  correctly. 
(3)  Sketch,  in  outline  merely,  a  long  mature  branch. 

Label  correctly. 
3.  The  plan  and  development  of  the  tree. 

a.  Compare  the  arrangement  of  the  branches  and  buds  on 

a  small  tree  with  those  of  the  branches  just  studied. 
Are  the  branches  grouped  on  the  tree  trunk  as  the 
smaller  branches  and  twigs  are  grouped  on  the  main 
axis  of  a  branch  ?  Compare  the  tree  with  the  larger 
branch  sketched  above.  Did  these  groups  of  branches 
on  the  main  trunk  arise  originally  from  lateral  buds 
as  on  the  branch  studied  above  ?  Why  are  they 
called  false  whorls  of  branches,  instead  of  true 
whorls  ?  Are  there  smaller  branches  on  the  trunk 
between  the  false  whorls  of  vigorous  branches  ? 
Compare  the  spruce  and  the  pine  in  this  respect. 
How  do  you  account  for  the  naked  portions  of  the 
trunk  of  the  pine  between  the  false  whorls  of 
branches  ?  How  do  you  account  for  the  naked  trunk 
below  the  lowermost  branches  ? 

b.  Observe  the  spruce  and  the  pine  from  a  short  distance. 

Can  you  determine  the  limits  of  the  last  season's 
growth  at  the  apex  of  a  tree  ?  How  many  buds 
grew  last  season,  including  the  terminal  bud  and 
those  which  produced  vigorous  lateral  branches  ? 
Can  you  determine  the  limits  of  each  season's  growth 
along  the  tree  trunk  ?  Where  are  the  nodes  and 
internodes  on  the  main  central  axis  of  the  pine  or 
the  spruce  ? 

c.  Sketch   the   last  three   or   four  years'  growth   at  the 

extreme  apex  of  a  pine  or  a  spruce.  Label  the  parts 
correctly. 


BIOLOGY  OF  HIGHER  SEED  PLANTS  13 

d.  Summarize  the  relation  of  the  following  factors  in  the 
development  of  the  conical  form  and  the  false  whorls 
in  the  spruce  and  pine: 

(1)  The  number  and  position  of  the  buds  that  grow 

each  season. 

(2)  The  spiral  plan  of  the  pine  and  the  spruce,  and  its 

relation  to  the  false  whorls  of  branches. 

(3)  The  effects  of  pruning.     Consult  the  text  (pp.  19 

and  20)  on  the  development  of  the  pine. 

THE  AMERICAN  ELM 

Select  a  terminal  shoot  of  an  elm  representing  three  or  four 
years  of  growth,  and  observe  the  following  points,  as  in  the 
pine  and  spruce  just  studied : 

1.  The  plan  and  development  of  an  elm  branch. 
a.  Leaves  and  buds. 

(1)  Compare  the  leaf  and  bud  arrangement  on  the  elm 

branch  with  that  of  the  lilac,  ragweed,  and  spruce. 
Are  the  leaves  and  buds  in  the  elm  arranged  like 
those  of  any  one  of  the  plants  thus  far  studied  ? 
Is  the  leaf  arrangement  favorable  to  the  maximum 
exposure  to  light  ?  Observe  an  entire  elm  branch 
from  above.  Observe  the  leaf  petioles.  Do  they 
curve  so  as  to  bring  all  of  the  leaves  in  one 
plane  ?  Observe  the  buds.  Is  there  a  true  ter- 
minal bud  or  is  it  subtemiinal,  that  is,  just  below 
the  apex  of  the  shoot  ? 

(2)  Sketch  a  single  terminal  twig  of  the  elm  to  illus- 

trate the  arrangement  of  buds  and  leaves  and  the 
light  relation  of  the  leaves.   Label  parts  carefully. 
1.  Seasonal  growth  of  buds  and  branches. 

(1)  Determine  the  age  of  the  main   axis  and   of  the 
lateral  branches  by  means  of  bud-scale  scars. 


14  LABORATORY  AND  FIELD  EXERCISES 

(2)  Study  the  annual  growth  of  the  main  central  axis  and 

of  the  larger  lateral  branches.  How  many  seasons 
of  growth  in  length  are  represented  in  each  ? 

(3)  How  many  buds,  including  the  subterminal  and 

lateral  buds,  grew  to  produce  the  central  axis  and 
lateral  branches  of  the  last  season's  growth  at  the 
end  of  the  shoot  ?  How  many  buds,  including  the 
subterminal  and  lateral  buds,  grew  into  branches 
in  each  of  the  previous  seasons  represented  on 
the  shoot  you  are  examining  ?  Is  there  a  general 
similarity  in  the  number  and  size  of  the  branches 
produced  each  season  ?  Did  the  main  axis  of  the 
branch  grow  equally  each  season  ?  (See  Fig.  6.) 

c.  Vigorous  buds  and  branches.    Are  the  larger  branches 

produced  at  about  the  same  place,  and  are  there 
approximately  the  same  number  each  season  ?    Is 
there  any  similarity  in  the  number  and  position  of 
weaker  branches  produced  annually  ? 
(1)  Study  the  buds  laid  down  on  the  main  axis  and 
the  lateral  branches  for  next  season's  growth. 
Are  some  larger  than  others  ?  Have  these  larger 
buds  the  same  relative  position  as  the  stronger 
branches  on  the  annual  growths  of  previous  years  ? 
As  the  branch  grows  larger,  what  becomes  of  the 
vigorous  lateral  branches  and  of  the  weaker  ones 
of  each  season?    Observe  a  large  branch  to  deter- 
mine this  point. 

d.  Comparisons.    Compare  the  elm  branch  and  that  of  the 

spruce  or  pine  already  studied  as  regards  the  annual 
growth  of  buds  into  branches.  To  what  do  the  vigo- 
rous seasonal  branches  of  the  elm  correspond  in 
the  pine  ?  Did  you  find  anything  in  the  pine  or  spruce 
corresponding  to  the  weaker  annual  branches  in  the 


BIOLOGY  OF  HIGHER  SEED  PLANTS  15 

elm.  ?  Be  able  to  explain  any  difference  observed  in 
this  respect.  As  the  elm  branch  grows,  what  becomes 
of  the  stronger  and  the  weaker  branches  ? 
e.  Drawing.  Remove  the  leaves  from  the  branch  under 
observation.  Draw  the  entire  branch  in  outline, 
indicating  clearly  the  following  structures : 

(1)  The  limits  of  each  season's  growth  in  the  length  of 

the  main  axis  and  the  lateral  branches. 

(2)  The  vigorous  and  the  weaker  branches  of  each  season. 

(3)  The  vigorous  and  the  weaker  buds  in  the  terminal 

twig  of  the  main  axis  and  one  or  two  lateral 
branches. 

2.  The  plan  and  development  of  the  tree.    Study  young  and 
mature  elm  trees  in  the  field,  beginning  observations 
with  a  young  elm. 
a.  Younj  elms. 

(1)  Observe  carefully  the  main  trunk  or  central  axis 

of  a  young  elm  and  the  arrangement  of  the 
branches.  Compare  the  arrangement  of  the  vigor- 
ous and  the  weaker  branches  of  the  tree  with 
that  of  the  branch  studied  above.  Can  you 
determine  the  limits  of  annual  growth  on  the 
main  trunk,  as  you  can  on  a  branch,  by  the  vigor- 
ous lateral  branches  produced  each  season  ?  Are 
the  weaker  branches  being  pruned  by  shading  ? 
Consult  Fig.  6  and  the  text  discussion  on  page  21. 

(2)  Do  you  find  anything  corresponding  to  the  false 

whorls  of  branches  of  the  pines  and  spruces? 
How  does  the  elm  differ  from  the  latter  trees 
in  the  production  of  false  whorls  of  vigorous 
branches  ?  Did  the  trunk  of  the  elm  below  the 
present  branches  ever  have  lateral  branches  ?  If 
so,  why  is  the  trunk  smooth  now  ? 


16 


LABORATORY  AND  EIELD  EXERCISES 


FIG.  6.    Growth  of  the  American  elm,  an  illustration  of  the  spreading 
type  of  trees 

The  letters  from  left  to  right  show  several  stages  in  the  development  of  the 
elm.  The  ultimate  form  is  determined  by  the  hody  plan,  the  method  of  bud 
growth,  and  the  pruning  effects.  The  corresponding  letters  on  each  figure  in- 
dicate the  vigorous  (and  so  successful)  branches  produced  each  season.  For 
further  discussion  consult  the  text 

(3)  Sketch  a  young  elm  to  show  the  vigorous  branches, 
which  correspond  to  false  whorls  in  the  pines, 
the  annual  growths  in  the  length  of  the  main 
axis,  and  the  weaker  branches.  Indicate  also  the 
scars  or  other  markings  where  branches  have 
already  been  naturally  or  artificially  pruned. 


BIOLOGY  OF  HIGHER  SEED  PLANTS  IT 

b.  Older  elm  trees. 

(1)  Examine  older  trees  of  the  American  elm  with  the 
points  iii  view  which  you  observed  above  in 
young  elms.  Is  the  main  crown  of  an  old  elm 
tree  formed  entirely  from  the  so-called  false  whorls 
of  vigorous  branches  laid  down  in  the  young  elm  ? 
Study  the  mode  of  growth  of  the  main  branches 
from  base  to  apex.  Do  they  repeat  in  their  growth 
the  history  of  the  tree?  Consult  Fig.  6  (a-/), 
and  Figs.  12  and  25  of  the  text. 

c.  Summary.     Summarize    briefly    the    part    played    by 

each  of  the   following   factors   in   the   development 
of  the  elm : 

(1)  The  spiral  body  plan  and  the  differences  in  the  buds 

produced  each  season  as  regards  size  and  vigor. 

(2)  The  unequal  growth  of  the  buds  each  spring  and 

the  difference  in  the  development  of  the  branches 
produced  by  them. 

(3)  The  effects  of  natural  and  artificial  pruning. 

(4)  The  annual  leaf  display. 
Consult  the  summary  in  the  text  (p.  23). 

SUPPLEMENTARY  THEE  STUDIES 

Some  trees  illustrate  the  above  principles  relating  to  tree 
development  more  strikingly  than  the  elm.  This  is  particularly 
true  of  young  Norway  maples  and  the  Carolina  poplar.  Study  the 
development  of  these  and  other  deciduous  trees  with  reference  to 
the  three  principles  deduced  from  the  study  of  the  pine  and  the 
elm.  These  principles  are  the  body  plan  or  arrangement  of  leaves, 
buds,  and  branches ;  the  unequal  vigor  and  growth  of  buds  and 
branches ;  the  effects  of  pruning  in  eliminating  all  but  the  most 
vigorous  branches,  which  then  occur  in  false  whorls  resembling 
those  of  the  pine. 


18  LABORATORY  AND  FIELD  EXERCISES 

B.   ADJUSTMENT   TO  THE  ENVIRONMENT 
THE  EMBRYO  AND  SEEDLING  OF  THE  BEAN 

1.  Structure  of  the  seed  and  embryo. 

a.  Eemove  the  protective  seed  coat  from  a  soaked  seed  of 

a  garden  bean  and  study  the  embryo.  The  parts  of 
the  bean  embryo  are  similar  to  those  of  the  pea 
(Fig.  13  of  the  text).  Compare  with  A  and  B,  Fig.  7. 

b.  Find  the  two  large  food-storing  leaves,  or  cotyledons, 

comprising  the  bulk  of  the  embryo.  Remove  one 
cotyledon.  Observe  the  plumule,  or  terminal  bud  of 
the  embryo,  composed  of  two  or  three  delicate  leaves. 
Find  also  the  hypocotyl,  or  stem  which  bears  both 
cotyledons  and  plumule.  The  first,  or  primary,  root 
also  grows  from  the  end  of  the  hypocotyl. 

c.  Draw  the  parts  of  the  embryo  as  they  appear  with  one 

cotyledon  removed. 

2.  Adjustment  of  the  embryo  by  tropisms  or  movements. 

a.  Emergence  of  the  embryo  from  the  soil.    How  is  this 

accomplished  ?  Sketch  a  plant  which  has  just  emerged 
from  the  soil,  indicating  the  position  assumed  by  the 
various  organs.  Contrast  the  bean  with  the  pea  and 
morning-glory  (Fig.  7).  Label  correctly. 

b.  Adjustment  of  the  organs  of  the  bean  to  the  environment. 

(1)  Study  two  or  three  stages  in  the  development  of 

growing  seedlings  of  beans.  Observe  the  changes 
in  the  position  of  hypocotyl,  epicotyl,  leaves,  and 
roots  as  development  proceeds, 

(2)  Sketch  the  most  mature  seedling  observed,  and  also 

younger  seedlings,  to  show  the  positions  assumed 
by  the  organs  at  each  stage.  Label  all  parts 
correctly. 


BIOLOGY  OF  HIGHER  SEED  PLANTS 
I 


19 


FIG.  7.   Seed  and  seedlings  of  morning-glory 

A,  section  of  seed,  showing  the  embryo  surrounded  by  the  endosperm ;  B,  C,  D, 

stages  in  the  development  and  adjustment  of  the  embryo  to  light  and  soil;  cot, 

cotyledons;  pi,  plumule 

c.  Special  motor  organs,  or  pulvini. 

(I)  Observe  the  pulvini  of  the  bean  leaves  (Figs.  15  and 
16  of  the  text).  How  do  they  differ  from  the 
remainder  of  the  petiole  ?  Study  the  form  of  the 
pulvinus  on  leaves  in  different  positions.  Do  you 


20  LABORATORY  AND  FIELD  EXERCISES 

observe  changes  in  the  form  of  the  pulvini  cor- 
responding to  the  positions  assumed  by  the  leaves  ? 
How  does  the  pulvinus  effect  the  movement  of 
the  leaf  blade  ? 
(2)  Draw  a  leaf  with  pulvini  greatly  magnified.    Label 

all  parts  of  your  drawing. 

d.  Naming  of  stimulus  and  response.  Label  the  parts  of 
the  largest  seedling  drawn  in  such  a  manner  as  to 
indicate  the  tropism  and  response  of  each  organ  in 
accordance  with  the  nomenclature  given  on  page  30 
in  the  text. 
3.  Experiments.  Observe  the  following  experiments  on  the 

tropisms  of  the  bean  seedling : 

a.  Place  one  growing  seedling  of  a  bean  in  a  horizontal 
position,  and  another  in  an  erect  position,  in  a  place 
where  the  lighting  will  be  uniform  on  all  sides. 
Observe  at  successive  laboratory  periods  until  both 
plants  are  adjusted  in  their  positions.  Write  up  the 
experiment  after  the  following  plan,  indicating  actual 
results  by  drawings  properly  labeled  to  indicate  the 
kinds  of  stimuli  and  the  nature  of  the  response  in 
each  instance. 

(1)  Object  in  view  in  performing  the  experiment.    What 

do  you  expect  to  prove  ? 

(2)  The  method  and  conditions  under  which  the  experi- 

ment is  performed.  Make  outline  drawings  of  the 
two  plants  to  indicate  the  position  of  leaves  and 
stems  at  the  beginning  of  the  experiment. 

(3)  Actual  results  observed  on  each  plant  after  several 

hours.  State  the  changes  observed  in  each  plant. 
Indicate  these  changes  by  outline  drawings.  Ex- 
plain the  mechanism  of  the  response  in  the  case 
of  each  organ.  Label  each  organ,  indicating  the 


BIOLOGY  OF  HIGHER  SEED  PLANTS  21 

nature  of  the  stimulus  and  response ;  for  exam- 
ple, apogeotropic.  Consult  the  text  discussion 
(pp.  28-31)  concerning  the  mechanism  of  response 
in  plants  and  the  naming  of  stimulus  and  response. 
(4)  Conclusions.  State  briefly  your  conclusions  from 
the  above  experiment  as  to  the  relations  existing 
between  the  bean  plant  and  some  of  the  forces 
of  the  environment. 

b.  Place  two  plants  before  a  window.    Rotate  one  on  a 

clinostat.  Observe  and  record  as  indicated  above 
after  several  hours,  when  the  plants  have  become 
adjusted  to  the  new  environmental  conditions. 

c.  TJie  gravity  sense.    Observe  germinating  seeds  of  corn 

or  beans  with  protruding  roots  which  are  rotated  on 
a  clinostat,  as  in  Fig.  18,  a-d,  of  the  text.  Compare  the 
position  assumed  by  the  rotated  roots  and  hypocotyls 
with  positions  taken  by  these  organs  in  seeds  pinned 
to  a  stationary  disk,  Record  the  object,  method, 
results,  and  conclusions  as  in  experiment  a,  above. 

SUPPLEMENTARY  STUDIES 

Adjustments  of  common  plants  to  the  environment.  Observe 
common  plants  in  the  field  and  in  the  laboratory,  and  record  the 
positions  assumed  by  the  various  organs.  Eecord  the  results  of 
your  observations  and  your  conclusions  in  a  manner  similar  to 
tluit  indicated  above  for  writing  up  experiments  on  movements. 
The  dandelion  (Taraxacum\  white  sweet  clover  (Melilotiis), 
cultivated  geranium,  and  some  climber,  such  as  the  ivy,  are 
good  species  for  observation.  At  least  one  such  plant  should 
be  assigned  to  each  student  to  work  up  independently  and  hand  in 
with  appropriate  drawings  and  notes. 


SECTION  II.   CELL  STRUCTURE  AND  GROWTH 

A.   THE  CELLULAR  STRUCTURE  OF  PLANTS 

1.  Mounting  sections.   Mount  sections  of  cork,  pith,  or  similar 

materials  as  follows  for  microscopic  observation  :  Clean 
a  slide  and  cover  glass  as  directed  by  an  instructor. 
With  the  point  of  your  scalpel  or  with  a  small  brush 
place  a  section  of  pith  or  cork  in  the  center  of  a  glass 
slide.  Add  a  drop  of  alcohol  with  a  pipette.  Take  a 
clean  cover  glass  with  forceps,  or  grasp  it  by  its  edges 
between  thumb  and  forefinger.  Place  one  edge  of  the 
cover  glass  on  the  slide  at  the  edge  of  the  drop  of  alcohol 
and  gently  lower  the  cover  glass  over  a  specimen. 
This  method  of  placing  a  cover  glass  over  an  object 
avoids  air  bubbles,  which  appear  under  a  cover  glass  as 
dark  rings  with  light  centers.  Now  observe  your  section 
with  the  compound  microscope  as  indicated  below. 

2.  Low-power  study.   Place  the  section,  mounted  as  directed 

above,  on  the  stage  of  the  microscope  for  observation. 
Adjust  your  mirror  until  you  have  a  white  field,  and 
make  the  following  observations  and  drawings: 

a.  Compare  the  appearance  of  your  section  with  that  of  a 

similar  section  of  a  honeycomb.  Is  it  made  up  of 
cells,  like  a  honeycomb,  with  similar  bounding  walls 
and  cavities  ?  Compare  your  section  with  a  piece  of 
honeycomb  if  the  latter  is  available. 

b.  Make  an  accurate  drawing  of  a  portion  of  your  section 

as  it  appears  under  a  low  power.  Label  the  parts 
with  appropriate  terms  corresponding  to  similar 
structures  in  a  honeycomb. 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


23 


c.  Who  made  the  first  observations  similar  to  the  one 
you  have  just  made  ?  What  conclusions  did  he 
draw  concerning  the  structure  of  plants  ?  Consult 
the  text  (Chapter  IV,  p.  54). 

3.  High-power  study.    Observe  a  portion  of  the  above  section 
under  high  power,  being  careful  to  secure  good  light. 


B  D 

FIG.  8.    Cell  and  tissue  differentiation  in  plant  organs 

A,  cross  section  of  a  root  with  dark  pith,  light  vascular  bundles,  and  dotted 
cortex ;  B,  cross  section  of  flower  stalk  with  tissues  as  in  A  but  with  an  outer 
layer  (dark)  of  thick-walled  strengthening  collenchyma  cells ;  C,  single-celled  alga 
with  nucleus  (n) ;  I),  cross  section  of  a  square-stemmed  plant  (col,  collenchyma, 
as  in  B ;  fv,  fibrovascular  bundles ;  pith  and  cortex  dotted) 

a.  Cell  ivalls.  Note  their  thickness,  color,  and  connections 
in  adjacent  cells.  Is  the  cell  wall  split  at  the  junc- 
tion of  adjacent  cells  to  leave  minute  spaces,  called 
intercellular  spaces  ? 

fi.  Cell  cavities.  Note  their  size,  shape,  and ,  contents.  Are 
the  cell  cavities  of  adjacent  cells  similar  in  these 
respects  ?  Do  the  cavities  of  these  cells  contain 
anything  besides  air  ? 


24 


LABORATORY  AND  FIELD  EXERCISES 


c.  Draw  two  or  three  cells  greatly  magnified  (half  an  inch 
in  diameter),  to  illustrate  the  parts  of  plant  cells  as 
seen  under  a  high  power.  Label  all  of  the  parts  of 
one  cell  carefully. 


CELL-WALL  THICKENING  AND  CELL  DIFFERENTIATION 

1.  Sections  of  celery,  corn,  or  a  similar  plant. 

a.  Cell  differentiation.     Observe  the  entire  section  with 

the  low  power  of  a  compound  microscope.  Are 
the  cells  in  different  parts  of  the  section  of  uniform 
size  and  form  ?  Why 
should  one  expect  to 
find  different  kinds  of 
cells  in  the  cell  col- 
ony which  makes  up 
the  structure  of  any 
stem,  leaf,  or  root  ? 
Observe  any  definite 
order  or  grouping  of 
similar  kinds  of  cells. 
Explain  such  group- 
ings on  the  basis  of 
use,  or  function,  in 
a  celery  or  corn  stalk. 
The  regular  oval  cell 
masses  are  vascular 
bundles,  which  con- 
duct water  and  foods  up  and  down  the  stem. 

b.  Make  an  outline  sketch  of  the  entire  section  as  it  ap- 

pears to  the  naked  eye  or  with  a  hand  lens.  Shade 
in  the  areas  showing  thick- walled  cells,  and  outline 
the  vascular  bundles.  Consult  Fig.  7.  Label. 


FIG.  9.  Epidermis  and  collenchyma 

ep,  epidermis;  col  (collenchyma),  the 
thick-walled  cortex  cells;    th,  thick- 
walled  portion  of  collenchyma  cell 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


25 


c.  Cell-wall  thickening.    Focus  with  a  high  power  on  some 

thick-walled  cells  in  the  section.  Observe  the  thick- 
ness of  the  cell  wall  and  the  size  of  the  cell  cavity. 
Are  there  intercellular  spaces  as  in  the  thin-walled 
pith  cells  ?  Consult  the  text 
concerning  the  mode  of  cell- 
wall  thickening  (p.  48). 

d.  Draw  three  or  four  thick- walled 

cells. 
2.  Vegetable  fibers  in  paper. 

a.  Examine    pieces    of    filter    paper 

and  newspaper  under  the  low 
power  of  a  compound  micro- 
scope. What  appears  to  be  the 
composition  of  the  paper  ?  Make 
a  rough  sketch  to  indicate  the 
structure  as  it  appears  under 
low  power. 

b.  Tease  out  a  small  piece  of  each 

kind  of  paper  with  needles  in 
a  drop  of  water  and  mount 
separately  on  the  middle  of  a 
glass  slide.  Cover  with  a  cover 
glass  and  study  with  both  low 
and  high  powers  of  the  com- 
pound microscope.  What  is  the  shape  of  these 
vegetable  fibers  ?  Have  they  a  cell  wall  and  a  cell 
cavity  ?  Compare  them  with  the  thick-walled  cells 
observed  in  celery. 

c.  Draw  two  or  three  fibers  accurately  from  each  specimen 

examined  and  label  their  parts.  Consult  Fig.  10  of 
these  exercises.  The  fibers  of  which  paper  is  made 
resemble  C  in  structure  and  in  shape. 


ABC 

FIG.  10.  Thick-walled 
fibrous  cells 

A,  tracheid   from  pine 

wood  ;  B  and  C,  fibrous 

cells 


26  LABORATORY  AND  FIELD  EXERCISES 

d.  What  is  the  function  of  thick-walled  cells  and  fibers  in 

plants?  What  function  do  they  serve  in  the  celery 
stalk  examined  above  ?  Why  is  a  cornstalk  hard  on 
the  outside  ?  What  makes  a  bamboo  fishing  rod  so 
strong  ?  What  is  the  nature  of  the  covering  of  hick- 
ory nuts  and  other  similar  nuts  ?  See  Figs.  8,  9  and 
10  of  these  exercises. 

e.  Summarize  the  functions  of  thick-walled  cells  and  vege- 

table fibers  in  plants,  and  state  some  of  their  important 
economic  uses. 


PROTOPLASM,  VACUOLES,  AND  NUCLEI  IN 
ROOT-TIP  CELLS 

1.  Study  of  the  text  and  sections.  Read  the  text  concerning 
the  nature  of  protoplasm,  vacuoles,  and  nuclei.  Study 
these  parts  of  the  cell  in  sections  of  root  tips  which 
have  been  previously  stained  and  mounted  for  this  pur- 
pose. Transverse  sections  of  root  tips  are  especially 
favorable  for  this  first  study  of  cells  with  protoplasmic 
contents. 

a.  Low-power  study.    Study  the  cells  immediately  beneath 

the  outer  bounding  cell  layer. 

(1)  Protoplasm  and  vacuoles.  Find  cells  in  different 
stages  of  vacuole  formation  as  described  in  the 
text  and  illustrated  in  Fig.  27.  Do  you  find  cells 
in  which  vacuoles  are  just  beginning  to  form  ? 
cells  in  which  the  vacuoles  are  large  light  spaces 
surrounding  the  nucleus  ?  cells  which  appear  to 
have  a  continuous  large  central  vacuole?  These 
may  be  found  in  deeper-lying  cells  of  the  section. 

b.  High-potver  study.    Select  a  favorable  cell  and  study 

the  following  structures  with  a  high  power: 


BIOLOGY  OF  HIGHER  SEED  PLANTS  27 

(1)  The  nucleus.    What  is  the  general  nature  of  the 

nuclear  protoplasm  ?  Does  it  appear  granular  or 
homogeneous  ?  Compare  the  nuclear  protoplasm 
with  the  regular  cell  protoplasm  or  cytoplasm. 
Can  you  detect  a  thin  nuclear  membrane,  or  wall, 
around  the  nucleus,  and  a  darker  granule,  the 
nucleolus,  within  the  nuclear  cavity  ?  Is  the 
nucleus  located  in  the  center  of  the  cell  ?  How 
is  it  supported  in  this  position  ? 

(2)  Vacuoles.    What  forms  the  bounding  walls  of  the 

vacuoles  ?  What  are  they  supposed  to  contain  in 
living  cells  ?  What  is  the  origin  of  vacuoles  and 
how  do  they  grow  ?  Consult  the  text. 

(3)  The  cytoplasmic  sac.    What  is  the  cytoplasmic  sac 

and  how  formed  ?  What  relation  does  the  cyto- 
plasmic sac  bear  to  the  general  protoplasm  of  the 
cell  ?  to  the  central  vacuoles  and  to  the  cell  wall  ? 

(4)  Draw  two  cells  greatly  magnified  (one  inch  in  diam- 

eter) to  illustrate  two  stages  in  the  formation  of 
vacuoles.  Put  details  of  the  nucleus  and  cytoplasm 
in  each  cell. 

CELL  STRUCTURE  AND  PROTOPLASMIC  STREAMING  IN 
STAMEN  HAIRS   OF    TRADESCANTIA   (SPIDERWORT) 

1.  Mount  some  of  the  delicate,  haiiiike  outgrowths  (stamen 

hairs)  which  grow  out  from  the  stamens  in  flowers  of 
Tradescantia,  the  common  spiderwort.  Preserved  ma- 
terial may  be  used  for  the  cellular  structure  of  the 
stamen  hair. 

2.  Low-power  study.    What  is  the  general  cellular  structure 

of  a  stamen  hair  ?  ,  How  do  the  cells  composing  it  differ 
in  size  and  form  at  the  smaller  apex  and  at  the  larger 


28  LABORATORY  AND  FIELD  EXERCISES 

basal  portion  of  the  hair  ?    How  are  the  cells  joined  at 

the  ends  ?   Have  they  cell  contents  ?    See  root-tip  cells. 

a.  Draw  a  figure  illustrating  the  form  and  appearance  of 

the  cells  of  a  stamen  hair  as  seen  under  low  power. 

Label  all  parts  observed. 

3.  High-power  study.  Select  large  cells  near  the  base  of  a 
stamen  hair  in  which  the  internal  structures  are  plainly 
visible. 

a.  Compare  the  structure  of  such  stamen-hair  cells  with 
that  of  root-tip  cells  as  regards  the  following  points : 

(1)  Cell  shape  and  outline.     How  do  stamen-hair  and 

root-tip  cells  differ  in  form  and  outline  ?  Can  you 
think  of  a  reason  for  the  differences  you  see  ? 
What  is  the  geometrical  form  of  a  stamen-hair 
cell  at  the  larger  basal  end  of  the  hair  ?  at  the 
smaller  apical  end  ? 

(2)  Cell  wall.    Is  the  cell  wall  smooth  or  roughened? 

thick  or  thin  ?   colored  or  colorless  ? 

(3)  'Cell  contents. 

(a)  The  nuclei.    Where  are  the  nuclei  located  in 

different  stamen-hair  cells  ?  Have  they  the 
same  position  in  all  cells  of  a  single  hair  ? 
Can  you  determine  by  focusing  whether  the 
nucleus  is  in  the  center  of  the  cell  or  next 
to  the  cell  wall  ?  Try  this  experiment  in 
different  cells.  Eesult  ?  Be  able  to  explain 
to  an  instructor. 

(b)  The  cytoplasm.    Do  you  find  cytoplasm  around 

the  nucleus  ?  How  is  it  disposed  in  other 
parts  of  the  cell  ?  Is  it  denser  in  some  areas 
than  in  others  ?  What  is  the  character  of  the 
cytoplasm  as  seen  under  high  power  ?  What 
parts  of  it  are  visible  ?  What  do  you  conceive 


BIOLOGY  OF  HIGHER  SEED  PLANTS  29 

to  be  the  structure  of  the  cytoplasm  in  these 
stamen  hairs  ?  Compare  with  root-tip  cells, 
(r)  The  vacuoles.  How  many  vacuoles  are  there  in 
the  stamen-hair  cells  ?  Are  the  cells  all  alike 
in  this  respect  ?  Is  there  a  cytoplasmic  sac  in 
all  stamen-hair  cells  ?  What  relation  does  the 
nucleus  sustain  to  the  vacuole  and  to  the 
cytoplasm  ? 

(4)  Draw  the  following  diagrams  of  a  stamen-hair  cell 
to  illustrate  its  form  and  structure :  Draw  the 
cell  as  it  appears  when  the  nucleus  is  in  focus. 
What  kind  of  view  of  the  cell  is  this  ?  Express 
this  view  by  an  appropriate  term.  Construct  a 
transverse  section  of  a  cell  as  it  would  appear  if 
cut  through  the  nucleus. 

4.  Living  stamen  hairs  and  protoplasmic  streaming.  Mount 
living  hairs  of  Tradescantia  in  water  and  observe  with 
low  and  high  powers  for  protoplasmic  movement. 

a.  Lmv-power  observations.    To  what  is  the  color  of  the 

stamen-hair  cells  due?  Can  you 'detect  the  nucleus 
and  the  protoplasmic  strands  ?  Select  a  good  cell 
for  observation,  and  focus  upon  it  carefully  with 
high  power. 

b.  Hlijli-power  study  of  living  protoplasm  and  its  movements. 

What  seems  to  be  the  nature  of  the  living  protoplasm 
of  a  stamen-hair  cell  ?  How  would  you  describe  it  ? 
Does  the  protoplasm  exhibit  movements  ?  Is  there 
one  general  movement  of  the  protoplasm  or  are  there 
several  streams  ?  Is  the  movement  definitely  related 
to  the  nucleus  ? 

c.  Draw  a  stamen-hair  cell  showing  the  position  of  the 

nucleus  and  cytoplasmic  strands.  Indicate  by  arrows 
the  direction  of  movement  of  the  protoplasm. 


30  LABORATORY  AND  FIELD  EXERCISES 

PLASTIDS  IN  PLANT  CELLS 

CHLOROPLASTIDS  IN  CELLS  OF  ELODEA  CANADENSIS 
(WATER  WEED) 

1.  Mount  in  water  young  leaves  of  Elodea  selected  from 
the  apex  of  Elodea  plants,  and  observe  as  follows : 

a.  Cellular  structure  of  the  Elodea  leaf. 

(1)  What  is  the  nature  of  the  cells  which  compose  the 

Elodea  leaf  ?  Are  they  uniform  in  size  and  shape  ? 
What  is  the  color  of  the  cell  walls  ?  What  is  the 
nature  of  the  cell  contents  ? 

(2)  Draw  ,an  outline  diagram  of  the  Elodea  leaf.    Indi- 

cate, by  lines  or  by  shading,  the  main  cell  areas 
of  the  leaf.  Fill  in  three  or  four  cells  of  each  area 
to  show  the  cell  structure  of  the  leaf. 

b.  Chloroplastids.    Observe  the  form  and  appearance  of 

the  green  grains,  or  plastids,  in  the  ElodeaAe&i  cells. 
Do  these  plastids  occupy  the  same  position  in  all 
the  cells'?  Is  there  any  regular  or  uniform  position 
assumed  by  the  plastids  ? 

c.  Protoplasmic  streaming.    This  is  usually  best  observed 

in  the  elongated  cells  composing  a  central  strand, 
or  midrib,  in  each  leaf. 

(1)  Observe  this   streaming  movement.    Is  there  one 

direction  for  the  movement  of  protoplasm  in 
different  cells  in  Elodea  ?  Does  the  protoplasm 
stream  from  cell  to  cell  through  the  cell  wall  ? 
Do  these  cells  have  a  cytoplasmic  sac  ? 

(2)  Draw  two  or  three  cells  of  Elodea  accurately,  indi- 

cating the  form  and  position  of  the  plastids.  Indi- 
cate directions  of  movement  by  means  of  arrows. 
Draw  two  or  three  plastids  greatly  magnified. 


BIOLOGY  OF  HIGHER  SEED  PLANTS  31 

d.  Composition  of  cJiloroplastids.  Select  shoots  of  Elodea 
which  have  been  previously  boiled  to  kill  the  plas- 
tids.  Place  one  or  more  shoots  in  a  test  tube  in 
ninety-five  per  cent  alcohol  and  observe  frequently. 
Does  the  alcohol  change  color  ?  "Why  ?  Allow  these 
test  tubes  to  stand  until  the  next  exercise.  Examine 
the  alcohol,  the  plants,  and  the  plastids.  Do  the 
plants  appear  to  be  somewhat  bleached  ?  Explain. 
What  are  the  parts  of  a  chloroplastid  ?  Answer  the 
above  questions  in  your  notes,  indicating  the  form, 
parts,  and  function  of  chloroplastids  in  cells  of  Elodea. 

CHROMOPLASTIDS 

1.  Examine  chromoplastids  in  the  cells  of  flowers  (for  ex- 

ample, Nasturtium)  and  fruits  (for  example,  tomato  and 
bittersweet  berries).  Draw  the  chromoplastids  examined. 

2.  See  the  text  discussion  of  the  structure  and  functions  of 

plastids. 

B.  CELL  STRUCTURE  AND  GROWTH 
GROWTH 

1.  Growth  of  root  tips  in  living  roots  of  corn  or  beans. 

a.  Observe  growing  root  tips  which  have  been  previously 

marked  with  uniform  millimeter  spacings  and  then 
allowed  to  grow  for  twenty-four  hours  or  more.  In 
what  part  of  the  root  tip  has  growth  taken  place  ? 
How  long  is  the  growing  zone  as  indicated  by  the 
millimeter  spaces  ?  Does  the  root  grow  at  the 
very  tip  ? 

b.  Draw  a  root  which  has  grown  in  the  manner  indicated 

above.    Indicate  the  length  of  the  millimeter  spaces 


32  LABORATORY  AND  FIELD  EXERCISES 

accurately.  Locate  the  rootcap  if  possible.  Consult 
the  text  on  the  parts  of  the  root  tip  and  label  your 
figure  correctly. 

2.  Cellular  structure  and  cell  growth  of  root  tips.  Select 
prepared  slides  cut  lengthwise  through  growing  root 
tips  and  study  the  cellular  structure  of  the  main  root- 
tip  areas. 

a.  Note  the  division  of  the  root  into  an  outer  epidermal 

cell  layer,  a  central  axis  cylinder,  and  an  interme- 
diate cortex,  each  composed  of  similar  cell  elements. 
Consult  the  text  figures  and  Fig.  11  on  the  structure 
of  the  root  tip. 

b.  Rootcap.    What  is  the  character   of  the   cells  of  the 

rootcap  ?  Do  its  cells  differ  at  the  extreme  apex  of 
the  root  and  at  its  upper  border  ?  What  is  the  geo- 
metrical form  of  the  rootcap  ?  How  is  it  related  to 
the  growing  meristem  cells  and  the  growing  cell 
zones  above  it  ?  What  is  the  function  of  the  root- 
cap  ?  How  is  it  renewed  when  worn  off  by  the  soil  ? 
•  c.  Meristem  layer.  What  is  the  form  and  extent  of  the 
meristem  cell  layer  ?  What  are  the  distinctive  char- 
acteristics of  its  cells  as  regards  size,  form,  and 
cell  contents  ?  Is  the  meristem  a  distinct  layer  of 
cells  or  do  its  cells  merge  into  the  cells  of  the 
rootcap  below  it  and  into  those  of  the  elongating 
zone  above  it  ? 

d.  Elongating  zone.  Study  the  cells  at  the  lower  and  upper 
margins  of  the  elongating  zone.  How  do  they  differ 
in  these  two  regions  from  the  cells  in  the  central 
region  of  the  elongating  zone  ?  Explain  the  changes 
which  you  note  in  the  cells  of  the  elongating  zone 
from  its  lower  to  its  upper  margin.  How  are  these 
changes  in  the  cells  brought  about?  How  is  the 


BIOLOGY  OF  HIGIIEll  SEED  PLANTS 


33 


elongating  zone  renewed  when  its  cells  become  con- 
verted into  cells  of  the  maturing  and  permanent 
zones  of  the  root  above  it  ?  Consult  the  text. 


FIG.  11.   The  growth  of  cells  in  a  root  tip 

a,  main  areas  of  the  root  tip,  shaded  ;  b-e,  camera  drawings  of  cells  from  the 

various  regions  of  the  root  as  indicated  in  the  figure.    Note  the  changes  in  form 

and  si/e  of  the  cells  as  growth  proceeds.  The  nuclei  grow  with  the  cells,  hut  they 

occupy  a  proportionately  smaller  part  of  the  cell  cavity  as  the  cells  enlarge 


Permanent  zone.  How  do  the  cells  above  the  elongating 
zone  differ  from  the  cells  below  them  in  form  and 
in  cell  contents  ?  Explain  the  changes  which  have 
taken  place  in  these  cells  with  their  growth. 


34  LABORATORY  AND  FIELD  EXERCISES 

f.  Drawings  of  cells  characteristic  of  each  root  zone. 

(1)  Select  a  small  group  of  about  three  cells  from  each 

zone  of  the  root,  and  outline  each  cell  group  on 
the  same  scale  as  that  shown  in  Fig.  11. 

(2)  Fill  in  the  details  of  cytoplasmic  and  nuclear  struc- 

ture in  a  group  of  cells  of  the  rootcap,  meristem, 
and  elongating  and  permanent  zones.  Indicate 
clearly  the  growth  of  vacuoles  and  the  origin  of 
the  cytoplasmic  sac  incident  to  growth.  See 
Fig.  11  for  the  proportionate  size  and  form  of 
cells  in  the  main  zones  of  the  root. 

3.  Elongation.   Read  the  discussion  in  the  text  on  the  method 

of  elongation  of  the  root  by  cell  division  and  growth. 
Summarize  the  facts  relating  to  the  cellular  growth  of 
the  root  in  length. 

4.  Structure  and  growth  of  buds. 

a.  Structure  of  buds.    Review  the  parts  of  the  bud  of  the 

lilac  as  seen  from  the  exterior.  Cut  median  vertical 
long  sections  of  buds  and  study  the  cut  surface  with 
a  hand  lens. 

(1)  Determine  the  parts  of  the  bud  and  their  relation 
to  each  other.  Is  there  an  apical  meristem  as  in 
roots?  Observe  the  relation  of  leaves  to  nodes 
and  internodes.  If  prepared  slides  are  available, 
observe  the  cellular  structure  of  the  above  por- 
tions of  a  bud.  Make  an  accurate  drawing  of  a 
long  section  of  a  bud  and  compare  it  with  that 
of  roots.  See  Figs.  37  and  40  of  the  text. 

b.  G-rowth  of  buds.    Observe  buds  which  are  expanding 

in  growth.  (Preserved  material  may  be  used  if  fresh 
is  not  available.)  What  is  the  general  method  of 
elongation  ?  Is  the  elongating  zone  in  buds  a  con- 
tinuous product  of  the  meristem,  as  in  the  root  ?  Is 


BIOLOGY  OF  HIGHER  SEED  PLANTS  35 

the  elongating  zone  in  the  bud  derived  from  a  meri- 
stem,  as  in  roots  ?  Be  able  to  explain  the  similari- 
ties and  differences  between  roots  and  sterns  in  these 
respects. 

c.  Summarize  in  your  notes  the  similarities  and  differ- 
ences between  root  growth  and  stem  growth  by 
means  of  buds.  Distinguish  between  the  growth  of 
woody  and  herbaceous  stems.  Consult  the  text  sum- 
mary (pp.  69-72)  on  the  growth  of  roots  and  stems. 

C.  THE  CELL  AND  CELL  DIVISION 

1.  Minute  structure  of  the  cell. 

a.  Select  a  well-stained   cell  in  the  cortical  region  just 

above  the  meristem  and  study  it  carefully  with  the 
highest-power  ocular  and  objective  available.  Read 
the  text  description  of  such  a  cell. 

b.  Do  you  see  any  indication  of  the  mesh  structure  of 

cytoplasm  mentioned  in  the  text  ?  What  is  the 
structure  of  the  chromatin  ?  Can  you  find  the 
nuclear  vacuole  surrounding  the  nucleolus  ? 

c.  Draw  the  cell  you  are  observing,  greatly  magnified,  to 

show  the  structure  of  the  cytoplasm  and  the  nucleo- 
plasm  (chromatin)  as  they  appear  in  your  section. 

d.  Observe  the  chromatin  in  other  nuclei  of  the  root  tip. 

Do  you  see  any  of  the  variations  in  its  structure 
noted  in  the  text  ? 

2.  Cell  division  (mitosis). 

a.  Prophase.  Select  a  nucleus  in  a  root-tip  cell  which 
shows  the  condensed  condition  of  chromatin  in  the 
form  of  chromosomes. 

(1)  Chromosomes.    Is  the  nuclear  membrane  still  pres- 
ent in  a  nucleus  with  chromosomes?    What  is 


LABORATORY  AND  FIELD  EXERCISES 

the  shape  and  color  of  the  chromosomes  ?  Are 
they  all  of  the  same  form  and  color  ?  Have  they 
any  definite  position  in  the  nucleus  with  refer- 
ence to  the  nuclear  membrane  ? 

(2)  Spindle.    Do  you   see   any  evidence   of  a   forming 

spindle  at  the  two  ends,  or  poles,  of  the  nucleus 
you  are  studying  ?  See  the  text  on  the  origin 
and  structure  of  the  spindle. 

(3)  Cytoplasm.    Is  the  cytoplasm  of  the  same  struc- 

ture around  the  nuclear  membrane  and  at  the 
periphery  of  the  cell  ?  If  any  difference  is  noted, 
in  what  does  the  difference  apparently  consist  ? 
What  is  the  apparent  structure  of  the  cytoplasm  ? 

(4)  Draw  a  cell  greatly  magnified  (1  or   2  inches  in 

length)  to  bring  out  the  above  points.    Draw  the 
chromosomes  very  accurately. 
b.  Metaphase. 

(1)  The  nucleus  and  the  nuclear  membrane.     Do   you 

find  any  definite  nuclear  membrane  and  nuclear 
cavity  in  the  metaphase  stage  ?  What  changes 
have  taken  place  in  the  nuclear  membrane  since 
prophase  ? 

(2)  The  chromosomes.    Has   their  form  changed   since 

prophase  ?  Have  the  chromosomes  a  definite  ar- 
rangement in  metaphase  ?  How  are  they  appar- 
ently supported  in  their  position  ?  If  you  could 
see  a  polar  view  of  the  chromosomes  in  meta- 
phase, what  arrangement  would  they  appear  to 
have  ?  Indicate  this  position  of  the  chromosomes 
in  an  outline  drawing. 

(3)  The  spindle.    Observe  the  spindle  carefully  with  a 

.  high  power.    What  is  its  apparent  structure?   its 
form?    Can  you  determine  any  definite  relation 


BIOLOGY  OF  HIGHEK  SEED  PLANTS  37 

of  the  spindle  fibers  to  the  chromosomes  ?  What 
relation  does  the  spindle  sustain  to  the  sur- 
rounding cytoplasm  ? 

(4)  Draw  a  metaphase  stage.  Outline  the  entire  cell. 
Draw  in  the  spindle,  the  chromosomes,  and  the 
cytoplasm  in  one  half  of  the  cell.  Label  accurately. 

c.  Anaphase. 

(1)  The  chromosomes.    Note  the  form  and  position  of 

the  chromosomes  in  anaphase.  How  have  the 
two  sets  of  daughter  chromosomes,  seen  in  ana- 
phase,  been  derived  from  the  single  set  observed 
in  metaphase  ?  Have  the  daughter  chromosomes 
the  same  form  as  the  mother  chromosomes  of 
metaphase?  Are  they  as  large  as  the  mother 
chromosomes  ? 

(2)  Tlie  first  spindle.    Are  there  spindle  fibers  between 

the  two  sets  of  daughter  chromosomes  ?  If  so, 
do  they  have  the  same  appearance  as  they  have 
in  the  polar  portions  of  the  spindle  ?  What  is 
meant  by  traction  and  supporting  fibers  of  a 
spindle  ?  Do  you  see  any  such  distinction  in 
the  fibers  of  the  anaphase  spindle  ? 

(3)  Draw  the  spindle  and  chromosomes  in  an  anaphase 

stage.  Label  all  parts  accurately.  Indicate  the 
position  of  traction  and  supporting  fibers. 

d.  Telophase. 

(1)  Early   telophase.     Observe,    if   possible,    an    early 

telophase  stage  in  which  the  chromosomes  are 

aggregated  at  the  poles,  as  described  in  the  text. 

(d)  Chromosomes.    Have  the  chromosomes  changed 

their  form  since  the  anaphase  stage  ?    What 

relation  do  they  sustain  to  each  other  ?    Are 

they  separated  or  joined  ? 

51U7 


38  LABORATORY  AND  FIELD  EXERCISES 

(b)  Spindles.    Are  the  spindle  fibers  still  present  in 

early  telophase  ?  Do  they  form  a  spindle  ? 
Are  these  fibers  a  part  of  the  original  spindle 
seen  in  metaphase  ?  If  so,  to  what  part  of 
the  metaphase  spindle  do  they  correspond  ? 
Do  you  observe  any  evidence  of  traction 
fibers  in  telophase  ? 

(c)  Draw  an  early  telophase  stage.    Label  all  struc- 

tures accurately. 

(2)  Late  telophase.  Select  cells  in  which  the  daughter 
nuclei  have  begun  to  form,  preparatory  to  cell 
division. 

(a)  Daughter  nuclei.  What  is  their  structure  ?  Have 

they  a  definite  nuclear  membrane  ?  What  is 
the  structure  of  the  chromatin  in  the  daughter 
nuclei  ?  Is  there  any  evidence  of  the  chromo- 
somes which  were  seen  in  early  telophase  ? 

(b)  The  second  spindle.    The  spindle  between  the 

daughter  nuclei  is  here  termed  the  second 
spindle,  to  distinguish  it  from  the  first  spindle, 
which  was  concerned  with  the  division  of  the 
nucleus  in  metaphase  and  anaphase.  What  is 
the  form  of  the  spindle  which  connects  the 
daughter  nuclei  ?  Are  the  fibers  evident  in  all 
parts  of  the  spindle  ?  Are  they  denser  in  one 
part  than  in  another  ?  Observe  dividing  cells 
in  which  the  equator  of  the  spindle  extends 
completely  across  the  cell. 

(c)  The  cell  plate.   Do  you  find  the  cell  plate  extend- 

ing across  the  equator  of  the  spindle  ?  Does 
it  stain  like  protoplasm  ?  What  is  its  sup- 
posed composition?  Does  the  plate  extend 
completely  across  the  cell  in  your  specimen  ? 


BIOLOGY  OF  HIGHER  SEED  PLANTS  39 

If  not,  find  a  cell  in  which  this  is  the  case. 
Note  the  relation  of  the  cell  plate  to  the 
spindle. 

(d)  The  cell  cytoplasm.    What  is  its  relation  to  this 

second  spindle  ?  Is  the  cytoplasm  reforming 
hetween  the  daughter  nuclei  ? 

(e)  Draw  a  stage  in  cell  division,  indicating  the 

structure  of  the  daughter  nuclei,  the  spindle, 
and  the  cell  plate.  Draw  the  cytoplasm  in 
one  half  of  the  cell.  Make  one  drawing  of 
the  spindle  and  cell  plate  in  which  the  cell 
plate  extends  completely  across  the  cell. 

SUPPLEMENTARY  STUDIES  IN  MITOSIS 

1.  Prophase.  Search  for  nuclei  which  illustrate  the  condensa- 
tion of  chromatin  from  the  resting  stage  into  the  chromo- 
some condition.  See  the  text  on  the  following  changes 
in  the  chromatin  during  prophase. 

a.  Irregular  dense  masses  of  chromatin.   Observe  and  draw 

one  or  more  nuclei  in  which  the  chromatin  has  con- 
densed into  irregular  dense  masses.  Is  there  any  definite 
arrangement  of  these  chromatin  masses  ? 

b.  Regular  spiral  arrangement.    Observe  nuclei  in  which  the 

chromatin  appears  in  a  regular  spiral  thread  in  the 
nucleus.  This  is  usually  termed  the  spireme  stage. 
Does  the  chromatin  appear  to  form  a  continuous  ribbon 
or  is  it  segmented  into  rods  or  chromosomes  ?  What 
changes  transform  this  ribbonlike  arrangement  of  chro- 
matin into  definite  chromosomes  ?  Is  there  any  evidence 
of  a  spindle's  being  formed  at  the  poles  of  the  nucleus 
you  are  examining  ? 

c.  Draw  the  nucleus  with  the  chromatin.    Indicate  the  begin- 

ning spindle  and  surrounding  cytoplasm,  if  the  spindle 
is  forming. 


40  LABORATORY  AND  FIELD  EXERCISES 

2.  Daughter  nuclei.   Observe,  if  possible,  one  or  more  stages  in 

the  transformation  of  daughter  nuclei  into  resting  nuclei. 
See  the  text  discussion  concerning  the  nature  of  these 
changes.  Draw  the  stages  of  daughter  nuclei  which  you 
find,  indicating  carefully  the  chromatin  changes. 

3.  Daughter  cells.   Do  you  find  young  daughter  cells  with  re- 

formed cytoplasm  and  nuclei  ?  How  was  the  cytoplasm 
reformed  between  the  daughter  nuclei  ?  Note  the  chro- 
matin and  the  nucleoli  of  the  daughter  nuclei.  Draw. 


SECTION  III.   ANATOMY 

A.  ANATOMY  OF  STEMS 
EXTERNAL  FEATURES  OF  WOODY  STEMS 

Review  the  following  important  external  features  of  shoots 
of  some  common  tree  like  the  ash  or  hickory.  See  your  pre- 
vious work  on  the  shoot  and  buds  of  lilac  and  elm. 

1.  Buds  and  their  relation  to  growth. 

a.  How  many  kinds  of  buds,  as  regards  position,  are  there 

on  the  shoot  you  are  studying  ?  Which  buds  are 
definitely  related  to  nodes  ?  Are  the  different  kinds 
of  buds  of  the  same  size  ?  How  many  buds  of  pre- 
vious years  grew  into  the  main  shoot  or  into  lateral 
branches  ?  Are  the  other  buds  still  alive  ?  Would 
they  ever  have  grown  into  branches  ? 

b.  Age  of  shoots.    Can  you  determine  how  many  years  of 

growth  are  represented  in  the  shoot  you  are  study- 
ing ?  How  are  the  yearly  segments  of  growth  marked 
off  ?  What  is  the  cause  of  these  markings  ? 

2.  The  bark  and  its  markings.    Is  the  bark  uniform  in  color 

and  appearance  in  the  older  and  younger  portions  of 
the  shoot,  representing  different  years  of  growth  ?  Peel 
off  or  scrape  off  the  outermost  thin  brown  skin  with  a 
scalpel;  what  is  the  color  of  the  tissue  beneath  it? 
Now  scrape  down  to  the  wood ;  do  you  find  any  new 
tissue  layers  comprising  the  bark  of  the  twig  ? 

3.  Scars  and  markings  on  the  bark. 

a.  What  large  scars  and  markings  do  you  find  on  the  bark 
of  the  entire  twig  ?    What  is  the  nature  and  position 

41 


42  LABORATORY  AND  FIELD  EXERCISES 

of  these  scars  and  markings  and  what  caused  them  ? 
Observe  the  bark  carefully  with  a  hand  lens ;  do 
you  tind  any  minute  markings  ?  Have  they  a  definite 
form  and  distribution  ? 

b.  Drawings.  Draw  a  portion  of  the  shoot  you  are  exam- 
ining, representing  three  years  of  growth  in  length. 
Indicate  clearly  the  appearance  and  position  of  the 
buds,  the  scars  marking  annual  growth  in  length, 
leaf  scars,  leaf-bundle  scars,  and  lenticels.  For  the 
meaning  of  these  terms  consult  the  text. 

GROSS  STRUCTURE  OF  MATURE  STEMS 

Study  wood  blocks  (preferably  oak)  cut  in  cross  and  in  long 
section  from  branches  of  trees.  To  give  the  best  results  these 
blocks  should  be  smooth  and  polished.  Observe  with  naked 
eye  and  hand  lens.  Consult  the  text  for  a  general  discussion 
of  the  structures  observed  below. 

TRANSVERSE  SECTIONS 

1.  Bark.   Compare  the  bark  of  a  mature  branch  in  sectional 

view  and  on  its  surface  with  that  of  the  twigs  observed 
above.  Is  the  epidermis  still  present  ?  the  green  bark  ? 
Compare  the  bark  of  a  branch  of  the  elm  with  that  of 
some  other  tree  in  wood  blocks.  What  kinds  of  tissue 
are  most  prominent  in  the  bark  on  the  branches  and 
trunks  of  trees  ? 

2.  The  cambium.    Locate  the  position  of  the  cambium  layer, 

represented  by  a  line  just  outside  of  the  wood. 

3.  The  wood  cylinder. 

a.  How  many  annual  growth  rings  are  represented  in  the 
block  you  are  examining  ?  How  is  the  boundary  line 
between  the  summer  and  spring  wood  of  successive 


BIOLOGY  OF  HIGHER  SEED  PLANTS  43 

years  marked?  What  is  the  relative  width  and 
texture  of  spring  and  summer  wood.? 

b.  Observe  the  number  and  extent  of  the  wood  rays ;  do 

they  all  extend  to  the  pith?  What  is  their  outer 
terminus  ? 

c.  The  pith.    Observe  its  size  and  shape. 

d.  Do  some  of  your  blocks  show  central  heartwood  and 

outer  sapwood  ?  Compare  two  or  three  different  kinds 
of  woods  as  regards  the  above  points,  if  specimens 
are  available. 


LONGITUDINAL  SECTIONS 

1.  Compare  longitudinal   sections  of  branches,  cut  in  both 
radial  and  tangential  planes,  with  the  above  transverse 
sections.    For  this  purpose  it  is  preferable  to  use  oak 
blocks  which  present  for  comparison  transverse,  longi- 
tudinal radial,  and  longitudinal  tangential  cut  surfaces. 
a.  Compare  as  follows  the  different  surfaces  of  wood  blocks 
prepared  as  indicated  above  : 

(1)  Determine   the    transverse,  radial,   and   tangential 

surfaces  of  a  wood  block.  Locate  corresponding 
structures  in  each ;  namely,  wood  rays,  annual 
rings  of  growth,  spring  and  summer  wood,  and 
heartwood  and  sapwood  if  present. 

(2)  What   are  the  distinctive    features    of   radial   and 

tangential  cuts  which  enable  you  to  distinguish 
them  ?  In  a  tangential  section,  is  a  wood  ray 
cut  across  its  long  axis  or  parallel  with  it  ?  In 
a  radial  section  ?  What  is  the  actual  form  of  a 
wood  ray  in  a  tree  trunk  ? 

(3)  Drawings.    Make    accurate   sketches    of  the  three 

surfaces  of  a  wood  block  to  show  the  wood  rays, 


Epidermis 

.Cortex 
^Phloem 
y-Xylem 


-Bark 
-Wood  ray 

Innual  ring 
-Pith 
Pruned 
branch 


rk  bark 

Cortex 
•Phloem 
-Xylem 
-Pith 

Wood  ray 
'Cambium 


Cork  bark 
•Phloem 
'ambium 

Summer  wood 

•ing  wood 
nnual  ring 
rptTFood  ray 


FIG.  12.   The  structure  and  growth  of  a  tree 

A,  diagram  illustrating  the  gross  anatomy  of  an  oak  tree  in  long  section.  Note 
the  relation  of  the  annual  rings,  the  junction  of  the  branches  •with,  the  main  trunk, 
and  the  covering  of  pruned  branches ;  B,  transverse  sections  of  the  tree  shown  in 
A,  at  three  levels.  The  figures  in  B  are  designed  to  illustrate  the  early,  or  pri- 
mary, structure  (a)  and  the  secondary  changes  (b,  c). 


BIOLOGY  OF  HIGHER  SEED  PLANTS  45 

annual  rings,  and  spring  and  summer  wood  as 
they  appear  in  transverse,  longitudinal,  radial,  and 
tangential  sections.  Indicate  ducts  by  circles, 
summer  wood  by  shading.  Label  these  structures 
in  each  view  of  the  block  drawn. 

PRACTICAL  EXERCISE 

Study  the  various  cuts  of  finished  woods  represented  in  the 
finished  woods  in  the  tables,  doors,  and  other  wood  furnishings 
in  the  laboratory.  See  Figs.  48  and  50  of  the  text  and  the  discus- 
sions concerning  the  structure  of  finished  woods. 

1.  Determine  the  different  cuts  of  wood,  namely,  the  radial, 

tangential,  and  transverse  cuts,  represented  in  the  finished 
woods  of  the  laboratory. 

2.  Determine  annual  rings,  heartwood  and  sapwood,  u  grain," 

"silver  grain,"  etc.  in  each  of  the  above  cuts. 

3.  Make  sketches  of  the  above  structures  in  transverse,  radial, 

and  tangential   sections   of   different  kinds   of   finished 
woods.    Label  all  structures  indicated  in  your  drawings. 

MICROSCOPIC  STRUCTURE  OF  WOODY  STEMS 
TRANSVERSE  SECTIONS 

Observe  transverse  sections  of  shoots  which  are  more  than 
one  year  old.  Use  only  hand  lens  and  low  power  in  your  first 
studies.  In  preparations  which  have  been  stained  with  a  red 
dye  (safranine)  the  wood  and  the  thick-walled  skeletal  tissues 
are  stained  red.  The  remaining  tissues  are  usually  stained  purple 
or  blue  with  logwood  dye  (heematoxylin). 

1.  General  tissue  layers  in  sections  of  living  shoots. 

a.  The  bark.  Note  the  limits  of  the  layers  designated  as 
brown  bark  and  green  bark  in  sections  of  fresh  twigs. 
Can  you  distinguish  the  epidermis  and  the  brown 


LABORATORY  AND  FIELD  EXERCISES 


cork  layer?  How  many  tissue  layers  of  different 
appearance  are  there  between  the  outer  cork  layer 
and  the  outer  limits  of  the  wood  ?  Observe  the  cells 
of  these  different  layers  with  a  low  power  and  note 
the  general  character  of  each.  Consult  the  text  and 


-PUh 


FIG.  13.    Healing  of  a  wound  due  to  the  severance  of  a  branch 

The  healing  is  done  hy  new  tissue,  called  callus,  formed  over  the  wound.   Ohservo 

the  irregularity  of  the  annual  rings  around  the  wound.   Redrawn  from  Curtis's 

"  Nature  and  Development  of  Plants  " 

Fig.  46  for  a  discussion  of  these  tissue  layers  belong- 
ing to  the  bark.    See  also  Fig.  52  of  the  text. 
b.  The  wood.    Note  the  following  main  tissues  and  struc- 
tures of  the  wood : 

(1)  Note  the  number  and  relative  cell  width  of  the  annual 
rings  of  growth;  the  distinction  between  spring 
and  fall  wood  ;  the  wood  rays.  The  relative  length 
and  termination  of  the  wood  rays  can  now  be 
accurately  traced.  Do  they  extend  through  the 
phloem  ? 


BIOLOGY  OF  HIGHER  SEED  PLANTS  47 

(2)  The  pith.  Note  the  irregularly  lobed  pith  in  some 
kinds  of  wood.  The  irregularity  of  the  pith  is  due 
to  the  effect  of  branches  and  leaves  on  the  form 
of  the  pith. 

c.  Draw  a  sector  of  the  section,  indicating  by  shading  and 
by  circles  the  different  layers  of  the  bark  and  wood. 
The  sector  should  be  three  or  four  inches  from  epi- 
dermis to  pith  and  two  inches  wide.  Draw  each  tissue 
layer  accurately  as  regards  its  relative  width  and 
extent,  but  do  not  draw  cells.  The  spring  ducts  may 
be  indicated  by  circles  and  the  summer  wood  by 
shading. 
2.  Cellular  structure  of  the  tissues.  (Use  prepared  slides.) 

a.  The  cork  (brown  baric).    Study  the   character  of  the 

cork  cells  and  compare  them  with  the  cork  cells 
studied  earlier  in  the  course.  Is  the  epidermis  still 
present  or  has  it  been  sloughed  off  after  the  formation 
of  cork  ? 

b.  The  cortex.    Note  its  limits  and  the  nature  of  its  cells. 

Do  its  cells  contain  protoplasm  and  chloroplasts  ?  Are 
there  intercellular  spaces  ? 

c.  The  phloem.    See  Fig.  52  of  the  text. 

(1)  Outer  phloem  layer.    Study  carefully  the  cell  walls 

and  the  contents  of  the  strengthening,  or  skeletal, 
layer  of  the  phloem  (stained  red  with  safranine). 
Can  you  find  cells  with  canal-like  perforations  of 
the  greatly  thickened  cell  walls  of  these  cells  ? 

(2)  Inner  phloem  layer.    Note  the  nature  of  its  cells  and 

their  gradual  merging  into  the  cambium  (see 
next  topic). 

(3)  Cambium.    The  cambium  is  composed  of  three  or 

four  cell  layers  adjoining  the  red  stained  wood 
on  its  inner  side  and  the  phloem  on  its  outer 


48  LABORATORY  AND  FIELD  EXERCISES 

border.  Determine  accurately  the  structure  of 
these  cambium  cells.  Note  the  orderly  arrange- 
ment of  the  tissues  of  the  xylem  and  phloem 
which  arise  from  the  cambium.  Why  is  this  so  ? 
Do  the  wood  rays  arise  similarly  from  the  cam- 
bium ?  Are  the  rays  continuous  from  the  time  of 
their  origin  to  old  age  in  a  tree?  Be  able  to 
explain  this  point. 

d.  The   wood.    Study    carefully  the  following  cells  and 
tissues  of  the  wood : 

(1)  Water   ducts.    Their    size,    contents,  and    cell-wall 

thickenings.  Why  are  they  so  much  larger  than 
the  surrounding  cells  ? 

(2)  Wood  fibers.    Are  they  thick-walled  or  thin- walled  ? 

Have  they  cell  contents  ?  What  is  their  function 
in  a  living  tree  trunk  ?  Are  they  structurally 
adapted  to  their  function  ? 

(3)  Annual  rings.    Study   the  relation    of   ducts   and 

fibers  at  the  junction  of  two  annual  rings.  Is  the 
boundary  line  between  spring  and  summer  wood 
a  sharp  one  ?  Why  is  the  annual  ring  so  plainly 
visible  in  stumps  or  sawn  logs  ? 

(4)  Wood  rays.    Observe  their  cell  structure  carefully 

and  compare  it  with  that  of  the  surrounding  dead 
ducts  and  fibers  of  the  wood.  Do  you  find  pores 
in  the  end  walls  of  these  cells  and  protoplasmic 
continuity  through  these  pores  ?  This  can  be  seen 
only  in  very  thin  and  well-stained  preparations. 
What  is  the  function  of  wood  rays  ? 

(5)  Wood  parenchyma.    Observe  the  amount  and  dis- 

tribution of  living  cells  with  darkly  stained  con- 
tents in  the  wood  outside  of  the  rays.  Are  these 
cells  in  isolated  or  in  connected  masses  ?  Are 


BIOLOGY  OF  HIGHER  SEED  PLANTS  49 

they  connected  with  the  wood  rays  ?    with  the 
ducts  ?    Do  they  have  cytoplasmic  and  nuclear 
contents  ?    What  is  the  function  of  these  cells  ? 
(6)  Drawings. 

(a)  Draw  a  small  portion  of  the  summer  and  spring 
wood  at  the  junction  of  the  two  in  an  annual 
ring.  Show  the  details  of  ducts  and  fibers. 
(&)  Draw  the  cambium  and  a  portion  of  the  phloem 
and  xylem  on  either  side  of  it,  including  at 
least  two  wood  rays.  Indicate  the,  orderly 
arrangement  of  the  tissues  which  arise  from 
the  cambium.  Draw  the  cells  and  tissues  with 
great  accuracy. 

LONGITUDINAL  SECTIONS 

Study  thin  longitudinal  sections  of  the  wood  of  oak,  birch, 
or  a  similar  woody  stem.    See  Fig.  53  of  the  text. 

1.  Select  a  portion  of  your  section  in  which  you  can  demon- 

strate most  clearly  the  following  main  wood  tissues  in 
long  section :  namely,  ducts,  fibers,  living  cells,  and 
wood  rays. 

2.  Study  and  draw  accurately  the  above  tissues  of  the  wood 

in  long  section.  Indicate  in  each  tissue  the  relative 
thickness  and  cell- wall  markings,  the  nature  of  the  cell 
contents  if  present,  and  the  shape  of  the  cells  com- 
posing the  tissue. 

3.  Observe  the  form  and  structure  of  the  cambium  cells  and 

the  phloem  cells,  consulting  the  text  figure.  These 
tissues  are  usually  too  difficult  for  accurate  delineation 
by  beginning  students. 


50  LABORATORY  AND  FIELD  EXERCISES 

HERBACEOUS  STEMS 
DICOTYLEDONS 

Study  the  main  layers  of  herbaceous  stems  in  transverse 
section,  contrasting  them  with  similar  layers  of  the  woody 
stems  studied  above. 

1.  Epidermis.    Is  the  epidermis  present  ?   What  is  the  color 

of  herbaceous  ste'ms  ?  Are  they  smooth  or  rough  ? 
Compare  the  external  features  of  woody  and  herba- 
ceous stems. 

2.  Bark.   What  are  the  layers  of  the  bark  (using  the  term  bark 

to  include  all  tissues  from  the  epidermis  to  the  cam- 
bium) ?  Contrast  these  tissue  layers  with  those  of  woody 
stems  just  studied.  What  is  the  function  of  green  bark  ? 

3.  The  wood  cylinder.    How  does  it  differ  from  that  found 

in  woody   stems  ?     Is    it   an   unbroken   cylinder  ?    Is 

it  as  thick  as  that  of  woody  stems  ?    Are  there  annual 

rings  ?    How  do    you    explain  your    findings   on   this 

point  ?  Stain  your  section  with  iodine  and  observe  again 

the  tissues  of  the  wood  cylinder.    Note  the  following : 

a.  Dead  tissues  and  cells.    Do  these  appear  to  be  similar 

to  those  of  a  woody-stemmed  plant  ?    If  they  are 

different,  be  prepared  to  explain  how  and  why.   Why 

can  an  herbaceous  plant  get  along  with  a  smaller 

amount  of  wood  tissue  than  a  tree  or  a  shrub  ? 

1>.  Living  tissues  of  the  wood.    How  are  these  distributed 

in  herbaceous  stems  ?   Compare  with  the  distribution 

of   similar  tissues  in   woody   stems.     Compare   the 

amount  of  living  storage  tissues  in  herbaceous  and 

woody  stems. 

c.  Pith.    Note  the   relative   size   of  the   pith  in    herba- 
ceous as  compared  with  woody  stems.    Is  there  a 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


51 


difference  be- 
tween the  two 
stem  types  in 
this  respect  ? 
4.  Drawing.  Draw 
a  sector  of 
an  herbaceous 
stem  in  out- 
line, to  show 
the  real  posi- 
tion and  rela- 
tive width  of 
the  main  tissue 
layers  of  the 
bark,  the  wood, 
and  the  pith. 
Label  each  of 
these  layers, 
using  terms 
corresponding 
to  those  pre- 
viously used  in 
the  study  of 
woody  stems. 
Point  out  the 
main  contrast- 
ing points  be- 
tween woody 
stems  and  her- 
baceous stems. 
Consult  the 
summary  in  the 
text  (p.  108). 


FIG.  14.  •  Transverse  (A)  and  longitudinal  (B) 

sections  of  the  stem  of  the  sunflower  (Helian- 

thus  annuus) 

A :  e,  epidermis ;  col,  collenchyma  of  the  cortex ; 
p,  parenchyma  of  the  cortex ;  b,  fibrous  phloem ; 
s,  sieve  portion  of  phloem  :  c,  cambium  ;  fv,  ducts 
of  the  xylem  portion  of  the  fibrovascular  bundles. 
B :  f,  fibers  of  the  xylem  ;  t,  dotted  duct ;  (,'  scalar- 
iform  duct ;  pa,  wood  parenchyma ;  t",  reticulated 
ducts ;  s,  spiral  ducts ;  p,  thin-walled  cells  of  the 
pith.  After  Miiller 


LABORATORY  AND  FIELD  EXERCISES 


5.  Summary  of  herbaceous  stem  structure.  Summarize  the 
distinctive  characteristics  of  herbaceous  as  compared 
with  woody  stems,  in  terms  of  bark,  cortex,  vascular 
cylinder,  and  pith. 

MONOCOTYLEDONS 

Study  transverse  sections  of  stems 
of  monocotyledons.  Contrast  their 
structure  with  that  of  herbaceous 
dicotyledons. 

1.  Is  there  a  distinct  bark  in  the 

stem  of  the  monocotyledon 
that  you  are  examining  ? 
a  distinct  wood  ring  and 
pith  ?  Do  you  find  xylem 
and  water  ducts  ?  Is  there 
phloem  connected  with  the 
xylem  ?  What  form  is  as- 
sumed by  the  masses  of 
xylem  and  phloem,  and  how 
are  these  masses  (vascu- 
lar bundles)  distributed  in 
the  stem  ?  Where  is  the 
strengthening  skeletal  tis- 
sue in  a  monocotyledonous 
stem  ?  the  storage  tissue  ? 

2.  Drawing.    Be  able  to  construct  a  drawing  of  a  stem  of 

a  monocotyledon  to  bring  out  the  contrasts  between 
its  structure  and  that  of  the  stems  of  herbaceous 
dicotyledons  examined  above. 

3.  Summarize  the  differences  between  the  stems  of  herba- 

ceous dicotyledons  and  monocotyledons. 


FIG.  15.    Structure  of  a  root  in 
transverse  section 

e,  epidermis ;    c,  outer  layer  of 

the  cortex  (cort) ;  x,  xylem,  and 

p,    phloem,    arranged    radially. 

After  Bonnier  and  Sablun 


BIOLOGY  OF  HIGHER  SEED  PLANTS  53 

B.   STRUCTURE  OF  ROOTS 

Study  transverse  sections  of  large  and  small  roots  and  com- 
pare their  structure  with  that  of  herbaceous  and  woody  stems 
of  dicotyledons. 

1.  Bark.    Do  roots  possess  a  definite  bark  ?    Has  the  bark 

(including  tissues  between  epidermis  and  cambium)  the 
same  general  layers  as  in  stems  ?  Are  these  layers  simi- 
lar in  arrangement  and  structure  in  stems  and  roots  ? 

2.  Xylem  and  pith.   Are  these  two  regions  the  same  in  roots 

and  stems  ?  Compare  young  and  old  roots  in  this  respect. 

a.  Dead   tissues  of  the  xylem.    Do   you  find    ducts  and 

fibrous  cells  ?    How  are  they  arranged  in  roots  ?  Are 
there  annual  rings  ? 

b.  Living  tissues  of  roots.  Are  these  more  or  less  abundant 

in  roots  than  in  stems?    Stain  fresh  root  sections 
with  iodine  to  demonstrate  this  point. 

3.  Cambium  and  phloem.    Are  these  tissue  layers  present 

in  the  root  section  that  you  are  studying  ?  Are  they 
as  evident  as  in  stem  sections  ? 

4.  Drawing.    Construct  a  drawing  of  a  root  in  transverse 

section  (no  cells),  to  illustrate  root  structure.  Label  the 
tissue  layers  correctly. 

5.  Summary.    Summarize  the   distinctive  features  of  root 

structure  as  compared  with  that  of  herbaceous  stems. 

C.   THE  STRUCTURE  OF  THE   LEAF 

For  the  preliminary  study  of  the  structure  of  a  leaf  use  thick 
leaves  of  Narcissus  or  onion,  which  are  easily  sectioned  in  a 
fresh  state. 

1.  Epidermis.  Peel  or  strip  the  epidermis  from  a  leaf  of  the 
onion  or  Narcissus.  Mount  in  water  or  dilute  alcohol 
and  study  its  cellular  structure. 


54 


LABORATORY  AND  FIELD  EXEECISES 


a.  Low-power  study.    Are  all  the  cells  of  the  epidermis 

alike  in  structure  and  form  ?  Do  they  have  chloro- 
plastids  as  a  part  of  the  cell  contents  ?  Do  they  differ 
in  this  respect  ? 

b.  A  high-power  study. 

Study  the  color- 
less and  the  green 
cells  of  the  epi- 
dermis very  care- 
fully with  a  high 
power.  Note  the 
shape  and  struc- 
ture of  each  kind 
of  cell.  How  many 
green  cells  are 
grouped  together  ? 
Are  they  separated 
by  a  solid  wall  or 

is    there    a    pore     _, 

IIG.  lo.  Transverse  section  of  a  leaf 


e,  elt  upper  and  lower  epidermis  with 
thick  outer  wall  (c)  and  stomate  (st) ;  p, 
palisade  cell  layer  with  intercellular  space 
(o)  below  the  stomate;  sp,  spongy  pa- 
renchyma with  intercellular  spaces  (i) ; 
ph,  phloem ;  x,  xylem  of  a  vein  in  section. 
After  Prantl 


between  them  ? 
c.  Drawing.  Draw  a  few 
cells  of  the  epider- 
mis of  the  leaf  ac- 
curately, indicating 
the  detailed  struc- 
ture of  thestomataand  the  surrounding  epidermal  cells. 
2.  Leaf  sections  of  a  fresh  leaf.   Study  transverse  sections  of 
leaves  cut  from  fresh  material.    Locate  the  main  tissue 
layers  of  the  leaf  in  such  sections  and  note  their  gen- 
eral character.    Use  low  power  and  dissecting  lenses 
in  the  study   of  these  thick    sections.    Is   the  green 
tissue  favorably  placed  for  receiving  light  rays?    Do 
you  find  the  veins  and  the  epidermis  ? 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


55 


a.  Make  a  general  drawing,  omitting  the  cells,  to  show  the 

position  of  the  epidermis,  green  mesophyll,  and  veins 

of   the   section 

which  is  under 

observation. 
I.  Epidermis. 

(1)  Note  its  color, 

thickness,  and 
extent  as  a 
covering  of  the 
leaf  surface. 
What  is  the 
real  form  of 
the  en  tire  epi- 
dermal layer 
of  the  leaf 
you  are  study- 
ing ?  Do  you 
find  stomata? 
Stomata  may 
frequently  be 

recognized  as  FIG.  17.  Conducting  cells  (tracheids)  of  the 
darker  places  veins  of  a  leaf 

in     flio    frocVi      «u>  midvein:  6,  lateral  veins ;  e,  termination  of 

111       lilt?       1 1  Coll  ,,          -,,       . 

veins ;  me,  areas  occupied  by  mesophyll  cells  in 
epidermis.  De-  the  living  leaf.  After  Sachs 

tails    of    the 

guard  cells  cannot  be  seen  in  such  thick  sections. 

(2)  What    special    structural    feature    of    the    epidermal 

cells  insures  against  the  loss  of  water?  Would 
the  same  structural  feature  serve  other  protective 
functions  ?  Search  for  sections  of  the  guard  cells 
and  of  the  pores  of  stomata.  Determine  the  pecul- 
iar cell  character  of  the  guard  cells, — for  example, 


56  LABORATORY  AND  FIELD  EXERCISES 

the  relative  thickness  of  the  cell  walls  as  well  as 
the  size  aud  the  living  contents  of  the  guard  cells. 

c.  Mesophyll. 

(1)  Note  the  character  of  a  mesophyll  cell  as  regards 
cell  wall  and  cell  contents.  Does  each  meso- 
phyll cell  come  in  contact  with  an  intercellular 
space  ?  What  would  be  the  advantage  of  such 
an  arrangement  ?  What  is  your  conception  of 
the  intercellular  system  of  a  leaf  ?  Is  it  a  con- 
tinuous aerating  system  or  are  the  spaces  seen 
in  a  transverse  section  isolated  spaces  ?  Do  you 
find  any  intercellular  spaces  immediately  above 
the  stomata? 

d.  Veins.    Study  the   structure   of  the  veins.    By  what 

kind  of  tissue  are  the  ducts  surrounded  ?  Is  there 
a  phloem  like  that  connected  with  the  xylem  of 
stems  ?  What  is  the  double  function  of  the  veins  in 
a  leaf  ? 

e.  The  skeletal  tissue.   Study  its  distribution  and  the  char- 

acter of  its  cells. 

/.  Drawing.  Construct  an  accurate  drawing  of  a  small 
portion  of  your  section  so  as  to  include  a  large  vein. 
Detail  the  tissues  of  the  epidermis,  mesophyll,  veins, 
and  skeletal  structures. 


SECTION  IV.   PHYSIOLOGY  OF  PLANTS 

INDIVIDUAL  AND  CLASS  EXPERIMENTS 

Two  classes  of  experiments  are  outlined  below :  namely, 
individual  experiments,  which  are  to  be  performed  by  each 
member  of  the  class,  and  demonstration,  or  class,  experiments, 
which  are  set  up  by  -an  instructor,  or  by  some  member  of  the 
class,  for  observation  by  all  members  of  the  class.  Both  kinds 
of  experiments  should  be  written  up  and  handed  in  as  a  part 
of  the  regular  laboratory  requirement.  Unless  otherwise  stipu- 
lated, all  experiments  should  be  written  up  in  the  following 
order : 

RECORDING  OF  EXPERIMENTS 

1.  Object  of  the  experiment.    State  concisely  the  object  of 

the  experiment. 

2.  Method.  State  the  method  used  in  the  experiment,  drawing 

apparatus  when  necessary  to  make  the  method  clear. 

3.  Actual  results  secured.    State  concisely  the  actual  results 

secured.    Do  not  include  theories  and  conclusions. 

4.  Conclusions.    What  does  the  experiment  seem  to  you  to 

prove  ? 

A.  PHOTOSYNTHESIS 

1.  The  presence  of  starch  in  leaves  of  Pelargonium  or  a  sim- 
ilar plant  with  white  areas.    Individual  experiment. 
a.  Compare  fresh  leaves  of  Pelargonium  with  leaves  which 
have  been  previously  boiled  and  treated  with  alcohol. 
Give  the  reason  for  the  difference  in  color.    Be  able 
to  explain  to  an  instructor. 
57 


58  LABORATORY  AND  FIELD  EXERCISES 

b.  Place  a  bleached  and  a  fresh  leaf  in  separate  watch 

glasses  and  flood  with  iodine  solution.  After  a  half 
hour  rinse  the  two  leaves  in  water  and  place  in  watch 
glasses  of  water  for  observation.  Test  some  starch 
with  iodine  in  a  watch  glass.  Compare  the  starch 
reaction  with  that  of  the  leaf.  Is  starch  present  in 
Pelargonium  leaves  ?  If  so,  where  is  it  located  and 
where  did  it  originate  ?  How  and  when  is  the  starch  in 
a  leaf  used  ?  Have  you  had  any  clue  to  the  answer 
to  this  question  in  your  work  with  woody  stems  ? 

c.  Record  the  object,  method,  and  results  of,  and  the  con- 

clusions to  be  drawn  from,  the  above  experiments, 
as  indicated  above  under  Recording  of  Experiments. 
Include  in  the  results  a  drawing  of  the  bleached 
leaf,  showing  the  distribution  of  starch. 

2.  Test  as  above  leaves  of  young  growing  corn  or  bean  plants 

about  six  inches  high.    Individual  experiment. 
a.  Use  two  plants  which  have  been  in  the  dark  overnight 
or  for  at  least  six  hours.     Why  is  this  precaution 
necessary  ? 

'  b.  Expose  one  plant  to  bright  sunlight  for  an  hour  or 
more  and  leave  another  in  darkness.  Remove  a  leaf 
from  each  plant,  boil,  extract  chlorophyll  with  warm 
80  per  cent  alcohol,  and  test  for  starch. 

c.  Results  ?   Do  the  two  leaves  show  a  different  reaction 

to  iodine?  If  so,  be  able  to  state  why.  What  im- 
portant conclusions  are  to  be  drawn  from  this 
experiment  ? 

d.  Record  your  results  and  conclusion  as  prescribed  above. 

3.  Gaseous  exchanges  in  water  plants  during  photosynthesis. 

Class  demonstration. 

a.  Observe  plants  of  Elodt><t  (water  weed)  which  are  ex- 
posed under  water  to  bright  sunlight.    Are  bubbles 


BIOLOGY  OF  HIGHER  SEED  PLANTS  59 

of  gas  given  off  ?  Shade  the  plant.  Do  the  gas 
bubbles  continue  ?  Explain,  Record  the  experiment 
by  the  usual  method. 

b.  Can  you  suggest  a  method  for  testing  the  gas  given  off 

by  Elodea  and  other  water  plants  when  exposed  to 
sunlight  ?  If  so,  perform  the  experiment  as  you  have 
planned  it. 

c.  Record   object,  results,  and  conclusions  in  the   usual 

manner. 
4.  Gaseous  exchanges  in  land  plants. 

a.  Place  three  tubulated  bell  jars  in  three  large  plates  or 

pans  which  will  hold  water.  Narrow-necked  bottles 
(Wolff-neck  bottles  are  good)  may  be  used  instead  of 
bell  jars.  Place  in  two  of  the  bell  jars,  or  bottles  if 
these  are  used,  vigorous  leafy  shoots  of  plants.  If  bell 
jars  are  used,  pour  water  into  the  plates  or  pans  until 
it  rises  an  inch  or  more  in  each  jar. 

b.  Lower  into  each  jar  or  bottle  a  lighted  candle,  and  cork 

tightly  with  a  rubber  cork  or  a  vaselined  common 
cork.  How  long  does  the  air  in  the  jars  support  com- 
bustion ?  Why  do  the  candles  go  out  ?  How  does  the 
burning  of  the  candles  change  the  composition  of  the 
air  in  the  jars  ?  Record  answers  to  points  (1)  and  (2) 
under  d. 

c.  Put  all  of  the  above  jars  in  sunlight  and  cover  one  con- 

taining a  leafy  plant  so  as  to  exclude  light.  After 
two  or  three  hours  lower  lighted  candles  into  each 
jar  and  test  quickly  to  see  whether  the  air  in  them 
will  support  combustion.  Is  there  a  difference  in  the 
air  in  the  jars  in  this  respect?  P>e  able  to  explain 
any  differences  observed. 

d.  Record  the  experiment  in  the  usual  manner.    Under 

Results  indicate  the  composition  of  the  air  in  the 


60  LABORATORY  AND  FIELD  EXERCISES 

three  jars  (1)  before  the  candles  are  placed  in  them, 
(2)  immediately  after  the  candles  cease  to  burn, 
and  (3)  at  the  close  of  the  experiment,  before  the 
corks  are  removed.  Explain  also  the  daily  gaseous 
income  and  outgo  of  the  exposed  and  the  covered 
plants  in  the  two  jars  during  the  period  of  the 
experiment.  How  and  why  would  they  differ  in 
this  respect? 

e.  Considering  the  results  of  the  above  experiment,  how 
do  plants  affect  the  air  of  a  living  room  by  day  ?  at 
night  ?  Is  it  healthful  to  have  a  large  number  of  plants 
in  a  living  room?  Give  reasons  for  your  conclusions 
concerning  this  matter. 

B.  RESPIRATION 

1.  Gaseous  exchange  of  plant  parts  during  respiration.    Indi- 
vidual experiment. 

a.  Select  two  bottles  or  pint  fruit  jars  with  wide  mouths. 

Put  into  one  bottle  or  jar  enough  dry  peas  or  beans 
to  cover  the  bottom.  In  the  second  receptacle  place 
a  similar  amount  of  germinating  seeds  after  they  have 
been  sterilized  in  a  weak  formalin  solution.  Test  the 
air  in  each  receptacle  with  a  burning  match  to  see  if 
it  supports  combustion.  Cork  air-tight  and  set  aside 
for  twenty-four  or  forty-eight  hours. 

b.  After  the  above  period  remove  the  corks  and  test  the 

air  again  with  a  lighted  match.    Result  ? 

c.  Write  up  the  experiment,  indicating  the  composition  of 

the  air  in  the  receptacles  at  the  beginning  and 
at  the  end  of  the  experiment.  Indicate  also  the  gase- 
ous income  and  outgo  of  the  seeds  in  each  jar  during 
the  time  of  the  experiment. 


BIOLOGY   OF  HIGHER  SEED  PLANTS  61 

d.  Class  experiment.  Treat  green  leaves,  stems,  buds,  or 
flowers  as  indicated  above  for  seeds.  Observe  and 
record  results  and  conclusions  at  the  end  of  the 
experiment  as  indicated  under  c.  What  precaution 
is  necessary  where  green  plant  parts  are  used  ? 

NUTRITION  AND  SEASONAL  LIFE 

1.  Study  the  seasonal  life  of  common  plants  like  the  potato, 

corn,  onion  or  tulip,  cherry  tree,  and  locust  tree, 
a.  Compare  the  seasonal  life  of  the  annuals  with  that  of 
the  bean  outlined  in  the  text;  that  of  the  biennials 
with  that  of  the  white  sweet  clover ;  that  of  the  per- 
ennials with  that  of  the  locust  and  the  apple. 

(1)  What  provision  does  each  plant  make  for  wintering  ? 

for  spring  growth  ?  for  summer  activities  and 
storage  ?  Are  the  same  physiological  functions 
characteristic  of  all  plants  at  the  same  season  in 
a  similar  habitat  ?  Be  able  to  state  the  main 
functions  or  activities  characteristic  of  the  plant 
in  winter,  spring,  summer,  and  autumn. 

(2)  Be  able  to  construct  drawings  similar  to  those  of 

the  text,  indicating  the  structures  by  which  plants 
winter  and  perform  the  activities  of  the  spring 
and  summer  seasons. 

(3)  Summarize  the  dominant  nutritive  activities  of  plants 

in  the  different  seasons.    See  Fig.  63  of  text. 

C.  TRANSPIRATION   AND  WATER  ASCENT 
TRANSPIRATION 

1.  Record  the  loss  of  water  from  a  leafy  shoot  placed  in  a 
graduate  or  in  a  potometer  made  from  a  burette.  Class 
experiment. 


62  LABORATORY  AND  EIELD  EXERCISES 

a.  Note  and  record  temperature,  general  light  intensity, 
and  relative  humidity  at  the  time  of  taking  each 
reading.  Take  records  at  convenient  intervals  for 
about  three  days. 

I.  Write  up  the  experiment  as  usual.  Under  Results  tabu- 
late your  readings  to  show  temperatures,  light  inten- 
sity, and  relative  humidity,  as  well  as  the  amounts 
of  water  lost  at  stated  periods  and  for  the  entire  period. 
c.  Summarize  the  main  factors  which  have  apparently 
caused  variations  in  the  rate  of  transpiration  in  your 
experiment  at  different  periods. 

2.  Record  the  loss  of  water  by  transpiration  from  a  potted 
plant,  as  for  the  previous  experiment,  and  record  results 
as  explained  above.  Class  experiment. 

WATER  ASCENT 

1.  The  path  and  rate  of  water  ascent.  Individual  experiment. 
Cut  off  leafy  herbaceous  shoots  or  stalks  of  celery  under 
water  and  add  eosin  to  make  a  strong  colored  solution, 
and  observe  as  follows :  • 

a.  Hate  of  water  ascent.  If  transparent  stems  of  Impatient 
or  bleached  stalks  of  celery  are  vised,  the  progress  of 
the  colored  solution  may  be  observed  in  the  stem  or 
in  the  leaf  veins. 

(1)  After  from  three  to  five  minutes  remove  the  stem 

from  eosin  and  make  cross  cuts  of  it,  beginning 
at  the  apex,  until  the  coloration  by  eosin  appears 
in  the  cross  section.  Measure  the  length  of  the 
stem  traversed  by  the-  solution  during  the  time 
it  was  left  in  eosin. 

(2)  From  the  above  data  determine  the  rate  of  ascent 

per  hour.   Compare  with  the  rates  of  water  ascent 


BIOLOGY  OF  HIGHER  SEED  PLANTS  63 

given  in  the  text.    Would  the  eosin  rise  in  the 
stem  as  rapidly  as  pure  water  ?    Kecord  results. 
b.  Path  of  water  ascent  in  the  stem  and  leaves. 

(1)  Cut  the  stem  lengthwise  through  a  node  and  trace 

the  path  of  the  eosin  from  the  main  stem  into 
the  leaves  and  branches. 

(2)  Draw  a  transverse  section  and  a  long  section  of  the 

stein,  indicating  the  tissue  in  which  the  eosin  solu- 
tion moved.  Did  it  pass  up  the  ducts  or  in  other 
tissues  of  the  xylem  and  phloem  ? 

(3)  Plot  the  path  in  the  leaf  veins  and  veinlets. 

ECOLOGICAL   RKLATIOX  OF  PLANTS  TO  WATER 

1.  Make  a  list  of   10  mesophytes,  10  hydrophytes,  5  xero- 

phytes,  and  10  tropophytes  from  the  wild  and  culti- 
vated plants  of  your  own  region.  Be  able  to  explain  the 
gross  structural  adaptations  of  these  plants  to  their 
habitat. 

2.  Are  some  of  the  above  plants  apparently  not  adapted  to 

their  present  habitat  ?  If  so,  how  do  you  explain  this  ? 
Be  able  to  give  the  essential  characteristics  of  the 
mesophytes,  hydrophytes,  xerophytes,  and  tropophytes 
of  your  region. 


SECTION  V.   REPRODUCTION 

A.   SEXUAL  REPRODUCTION 
THE  FLOWER  AXD  ITS  PARTS 

Examine  some  large  flower  like  that  of  the  mandrake  and 
note  the  nature  and  relation  of  its  parts. 

1.  How  many  kinds  of  different  parts  or  organs  are  there 

in  the  flower  ?  How  are  they  arranged  with  reference 
to  each  other  ?  Does  each  set  of  organs  form  a  circle, 
or  whorl,  like  cyclic  leaves  on  a  stem,  or  are  all  parts 
of  the  flower  spiral,  like  spirally  arranged  leaves  ?  Do 
any  portions  of  the  flower  resemble  leaves  in  color, 
form,  or  venation  ? 

2.  Remove  carefully  the  floral  parts  or  organs  on  one  side 

of  a  flower.    Place  the  parts  thus  removed  in  a  watch 
glass  of  water  for  future  examination.    Now  examine 
the  flower  from  which  the  parts  have  been  removed. 
a.  What  is  the  nature  of  the  floral  axis  to  which  the  floral 
parts  are  attached  ?  Has  it  nodes  and  internodes  ?   Is 
it  like  the  axis  of  a  branch  or  bud  in  this  respect  ? 
5.  Observe  again  the  relative  .position  of  the  different  sets 
of  organs  of  the  flower.    Are  the  members  of  each 
set  spiral  or  cyclic  in  arrangement  ?   What  kind  of 
organ  (or  organs)  terminates  the  floral  axis  ? 
c.  Does  the  flower  resemble  a  bud  in  the  arrangement  of  its 
organs  on  the  floral  axis  ?  Does  it  seem  to  you  possible 
that  the  flower  was  originally  derived  from  a  short 
branch  or  bud  ?   What  parts  of  the  flower  are  nearly 
like  leaves  ?    What  parts  are  highly  modified  ? 
64 


BIOLOGY  OF  HIGHER  SEED  PLANTS  65 

3.  Draw  the  entire  flower  as  it  appears  on  the  side  from 

which  the  parts  have  been  removed.  Indicate  accu- 
rately in  the  drawing  the  form  and  relative  position  of 
the  floral  parts  on  the  floral  axis. 

a.  Study  the  text  and  Figs.  215  and  84  and  name  the 
parts  of  the  flower  sketched  above. 

4.  The  essential  organs  of  the  flower. 

a.  Anthers  and  pollen.    Observe   carefully  with  a  hand 

lens  and  low  power  the  dehiscence  of  the  anther. 
Does  the  anther  sac  open  crosswise  or  lengthwise  to 
shed  the  pollen?  Do  you  see  the  dustlike  pollen 
grains  issuing  from  the  slit,  or  dehiscence  line,  of 
the  anther?  How  many  anther  sacs  are  there  in 
one  anther?  Draw  a  stamen  greatly  magnified  to 
show  the  mode  of  dehiscence  of  the  anther  sac. 

b.  Pollen.    Dust  some   pollen  on  a  slide  and   study   its 

form  and  structure.  Is  the  pollen  grain  a  cell  ?  Is 
its  wall  smooth  or  rough  ?  Can  you  see  any  cell 
contents?  Draw  the  pollen,  exterior  view,  as  it 
appears  to  you  in  your  specimen. 

c.  The  pistil 

(1)  Observe  the  external  parts  of  the  pistil  and  note 

their  form  and  structure.  Observe  the  stigma 
carefully.  Is  it  adapted  to  the  reception  and 
retention  of  pollen  ?  Draw  a  pistil,  including  an 
enlarged  view  of  the  stigmatic  surface,  and  name 
all  its  parts. 

(2)  Cut  a  transverse  section  of  the  upper  and  middle 

portions  of  the  ovary.  Cut  also  a  section  through 
the  style,  if  one  exists.  How  does  the  ovary 
differ  in  structure  at  the  different  levels  at  which 
you  have  cut  it  ?  How  is  the  wall  of  the  ovary 
modified  in  the  median,  or  middle,  section  of  the 


66 


LABORATORY  AND  FIELD  EXERCISES 


ovary  ?  Are  there  budlike  outgrowths  from  the 
enlargement  of  the  ovary  wall  in  your  section  ? 
What  is  the  shape  of  these  buds,  or  enlarge- 
ments? Draw  the  two  or  three  sections  of  the 
ovary  which  you  have  made.  Label  the  parts  after 
you  have 
studied  "the 
text  and 
Fig.  220. 

5.  The  fruit.  Study 
both  the  exter- 
nal and  the  in- 
ternal structure 
of  the  fruit  of 
the  mandrake 
or  other  plant 
examined.  Do 
you  find  the 
same  parts  in 
the  fruit  as 


FIG.  18.  Section  of  a  portion  of  a  wheat  kernel 


p,  pericarp;  t,   seed  coat;  al,   aleurnne,  or  ni- 

trogenous  layer    of  the   endosperm  ;    //,   nuclei  ; 

st,    starch-storing     cells     of     the      endosperm. 

After  Strasburger 


you  did  in  the 
pistil  ?  What 
forms  the  in- 
terior of  the  fruit  ?  Where  are  the  ovules  ?  the  placenta  ? 
the  ovary  wall?  What  relation  has  the  fruit  to  the 
pistil  ?  Define  a  fruit.  Draw  a  sectional  view  of  the  fruit 
to  show  all  of  its  parts  in  their  proper  relation.  Label 
the  parts,  using  the  same  terms  as  were  used  for  similar 
parts  of  the  ovary  (see  text  discussion  and  Fig.  221). 
6.  Supplementary  studies  :  gametogenesis,  fertilization,  and 

development. 

a.  Microscopic  structure  of  pollen.     Mount  large   pollen 
grains  taken  from  some  liliaceous  plant,  like  the 


BIOLOGY  OF  HIGHER  SEED  PLANTS 


67, 


-str 


tulip,  Narcissus,  or  Easter  lily.    Observe  them  care- 
fully under  low  and  high  powers  of  the  microscope. 

(1)  Does  the  pollen  cell  have  one  or  more  nuclei?  Do 

different  pollen  cells  differ  in  this  respect  ?  Do  you 
see  granu- 
lar cytoplasm 
surrounding 
the  nucleus 
in  some  pol- 
len cells  ? 

(2)  Draw   a  pollen 

cell  much  en- 
larged. Indi- 
cate the  gran- 
ular condition 
(Fig.  85,  a)  of 
the  cytoplasm 
and  the  rel- 
ative size  of 
the  nucleus, 
or  nuclei,  in 
the  cell.  La- 
bel your  fig- 
ure correctly. 
(.">)  Xtmly  of  pollen 
tubes.  If  pol- 
len tubes  are 

available,  study  the  structure  and  method  of 
formation  of  pollen  tubes.  Draw  a  pollen  cell 
and  its  pollen  tube.  Note  and  draw  the  structure 
of  the  tube  and  its  cytoplasmic  contents.  If  pos- 
sible observe  the  nuclei  in  the  pollen  tube.  This 
point  is  difficult  to  determine. 


-  -  -  ou  int 


FIG.  19.    Diagram  of  the  ovule,  embryo 

sac,    and    embryo    of    shepherd' s-purse 

(Capselkt) 

ou  int,  outer  integument ;  in  int,  inner  in- 
tegument ;  susp  c,  suspensor  cells ;  e  s  w, 
embryo-sac  wall ;  r  r,  root  region ;  st  r,  stem 
region ;  s  I,  seed  leaves.  From  Bergen  and 
Caldwell's  "Practical  Botany  " 


68  LABORATORY  AND  FIELD  EXERCISES 

b.  The  structure  of  the  ovule. 

(1)  Gross  structure.    Dissect    out   the   ovule   from   the 

ovary  of  some  common  plant  into  a  drop  of 
water  on  a  slide.  Mount  and  observe  the  essen- 
tial parts  of  the  ovule ;  namely,  the  f uniculus,  or 
stalk,  the  body  of  the  ovule,  and  the  micropyle. 
Ovules  of  the  shepherd's-purse  (Capselld),  when 
treated  with  a  weak  solution  of  potash,  will  often 
show  the  outline  of  the  embryo  sac  within  the 
ovule.  Draw  one  or  more  ovules  to  show  the 
structure  observed.  Label. 

(2)  Microscopic  structure  of  the  ovule.    If  material  is 

available,  study  thin  sections  cut  through  the 
ovule  to  show  the  embryo  sac  and  micropyle ; 
for  example,  in  shepherd's-purse  or  mandrake. 

(a)  Determine  the  structure  and  thickness  of  the 
seed  coats.  Do  you  see  the  micropyle  of  the 
ovule  ?  What  is  the  nature  of  the  large  cen- 
tral light  space  of  the  ovule  ?  Is  there  a 
nucleus  in  this  space?  Are  there  vacuoles 
and  cytoplasm  ?  Has  this  central  space  the 
structures  of  a  cell  ? 

(1}  Study  the  structure  and  position  of  the  embryo. 

(c)  Draw  the  sectional  view  of  the  ovule,  indicating 
the  micropyle,  the  cellular  structure  of  the 
ovule  coats,  and  the  form  and  structure  of 
the  embryo  sac  and  embryo. 

POLLINATION  IN  PAPILIONACEOUS  FLOWERS 

1.  Inflorescence,  or  flower  cluster.    Examine  an  inflorescence 

of  some  plant  belonging  to  the  pea  family. 
a.  Parts  of  the  inflorescence.    Has  the  inflorescence  axis 
the  same  parts  as  the  stem  axis  below  it;  namely, 


BIOLOGY  OF  HIGHER  SEED  PLANTS  69 

nodes  and  internodes  ?  Where  do  the  flowers  origi- 
nate on  the  axis  ?  Is  there  any  structure  below  the 
flower  stalk  corresponding  to  a  leaf  ?  To  what  part 
of  an  ordinary  leafy  shoot  would  a  flower  on  the 
inflorescence  axis  correspond  most  nearly,- —  to  a  leaf 
a  bud,  or  a  branch  ?  On  what  evidence  do  you  base 
your  conclusions  ?  See  Fig.  212  of  the  text. 
b.  The  inflorescence  and  pollination.  Are  the  open  flowers 
at  the  apex  or  at  the  base  of  the  inflorescence  ?  Is 
the  inflorescence  an  advantageous  arrangement  for 
securing  cross-pollination,  or  the  transfer  of  pollen 
from  the  anther  of  one  flower  to  the  stigma  of 
another  flower,  by  insects  ?  Compare  an  inflores- 
cence with  solitary  flowers  in  this  respect.  Sketch 
an  inflorescence  and  a  portion  of  the  stern  below  it. 
Name  the  parts  correctly. 

STRUCTURE  OF  PAPILIONACEOUS  FLOWERS 

STRUCTURE  OF  THE  FLOWER 

Examine  flowers  of  some  member  of  the  pea  family  and  com- 
pare their  structure  with  that  of  a  simple  flower  like  that  of 
the  mandrake. 

1.  Perianth.    How  many  whorls,  or  sets,  of  organs  in  the 

perianth  ?  Are  the  members  of  each  whorl  regular  or 
irregular  in  form  ?  How  many  parts  in  each  whorl  ? 
Are  the  parts  of  each  whorl  united  or  separate  ?  Remove 
the  parts  of  the  perianth  and  place  them  in  their  proper 
order  on  the  table.  Sketch  the  parts  of  the  corolla. 

2.  Essential  organs.    How  many  stamens  are  there  ?    Are 

they  separate  or  united?.  How  are  the  stamens  related 
to  the  pistil  ?  Study  the  form  and  external  features  of 
the  ovary,  style,  and  stigma.  Study  the  style  and  stigma 


70  LABORATORY  AND  FIELD  EXERCISES 

with  a  hand  lens.    What  is  the  nature  of  the  stigniatic 
and  stylar  surfaces  ?    Are  they  smooth  or  rough  ? 
3.  Remove  the  perianth  from  one  side  of  a  flower  so  as  to 
expose  the  essential  organs  in  their  natural  position. 

a.  Sketch  the  essential  organs  accurately  and  indicate  in 

outline  the  relation  of  the  perianth  to  these  organs. 

b.  Make  an  accurate  drawing  of  the  pistil,  indicating  the 

position  of  the  placenta  and  ovules  and  the  peculiar 
structure  of  the  stigma  and  style.  What  advantages 
are  there  for  pollination  in  the  structural  relations 
of  the  style  and  stigma  ?  Label  all  of  the  above 
figures  accurately.  See  Fig.  89  of  the  text. 

CROSS-POLLINATION 

Select  a  flower  of  some  member  of  the  pea  family  for  the 
following  experimental  study  of  cross-pollination : 

1.  Press  down  the  keel  petals  with  the  point  of  a  pencil  or 

with  a  dissecting  needle.  Eesult  ?  Where  would  an  in- 
sect need  to  alight  in  order  to  imitate  the  above  action 
of  the  keel,  stamens,  and  pistil  ?  If  an  insect  should 
visit  a  series  of  flowers  like  the  one  experimented  upon, 
would  cross-pollination  be  secured  ?  Be  able  to  explain. 

2.  Read  the  account  in  the  text  (p.  170)  on  cross-pollination 

in  the  common  locust  (Robinia  pseudo-acacia). 

a.  Does  the  flower  upon  which  you  experimented  possess 

the  contrivances  of  the  locust  flower  for  securing 
cross-pollination  ?  If  not,  in  what  respect  does  it  differ 
from  the  locust  ? 

b.  Construct  a  drawing  to  show  the  relation  of  the  anthers 

to  the  stigma  and  of  both  anthers  and  stigma  to  the 
keel,  when  the  latter  is  depressed.  Compare  the  figure 
with  your  first  figure  of  the  flower  with  one  half  of  the 
corolla  removed. 


BIOLOGY  OF  HIGHER  SEED  PLANTS  71 

3.  The  fruit  and  seed  in  members  of  the  pea  family. 

a.  Examine  the  fruit  of  the  pea,  beau,  locust,  or  some 

other  member  of  the  pea  family.  Compare  this  fruit 
with  that  of  the  pistil  already  studied.  Note  the 
corresponding  parts  of  fruit  and  ovary.  Be  able  to 
define  a  fruit  in  terms  of  the  pistil. 

b.  Remove  one  half  of  the  wall  (carpel)  of  the  fruit  and 

observe  the  form  and  attachment  of  the  seeds  to  the 
placenta.  Sketch  the  inner  view  of  the  fruit  or  pod 
with  the  seeds.  Label  the  parts  of  your  sketch  accu- 
rately, including  the  parts  of  the  seeds.  Use  the  same 
terms  as  those  used  for  the  pistil  and  ovules. 

4.  Examine  seeds  of  beans  or  of  the  locust.    How  has  the 

ovule  changed  to  form  the  seed  ?  What  advantages  are 
there  in  the  changes  ?  Do  you  find  the  scar  on  the  seed 
caused  by  the  breaking  off  of  the  funiculus  ?  Do  you 
find  other  marks  near  this  latter  scar  ?  Draw  an  exte- 
rior view  of  the  seed  on  the  side  of  the  hilum,  or  scar, 
caused  by  the  removal  of  the  funiculus.  Label  accurately. 

5.  Cut  thin  sections  from  the  cut  surface  of  the  cotyledon  of 

a  bean.  Stain  with  iodine.  Result  ?  What  is  the  func- 
tion of  the  cotyledons  ?  What  kind  of  reserve  food  is 
most  prominent  as  revealed  with  iodine  ?  Draw  a  portion, 
of  the  section  (Fig.  IS). 

SUPPLEMENTARY  STUDY 

Study  some  assigned  flower  or  flowers  with  reference  to  devices 
for  securing  cross-pollination.  Construct  drawings  to  indicate  the 
particular  devices  for  pollination  in  the  flower  or  flowers  examined. 


PART  II.   THE  PLANT  GROUPS 


SECTION  VI.   THALLOPHYTES  (ALG^  AND 
FUNGI) 

A.  THE  ALGJE 
PROTOCOCCUS  (PLEUROCOCCUS) 

1.  Habit  and  Habitat.    Note  the  appearance  of  Protococcus 

on  bark,  boards,  or  stones.  Has  the  green  incrustation 
any  definite  form  or  structure  comparable  to  that  of 
the  higher  green  plants  ?  Do  you  see  any  evidence  of 
roots,  stem,  or  leaves  ?  Do  you  know  whether  Proto- 
coccus ever  lives  in  water,  like  the  other  fresh-water 
algse  ?  Is  Protococcus  on  bark  or  stones  xerophytic  or 
mesophytic  in  habit  and  habitat  ? 

2.  Structure.    Scrape  off  a  little  of  the  green  incrustation 

formed  by  Protococcus  in  a  drop  of  water  on  the 
center  of  a  glass  slide.  Be  careful  not  to  remove 
pieces  of  bark  or  dirt  with  the  plants.  Cover  and 
press  out  gently  under  the  cover  glass  with  a  dissect- 
ing needle.  Examine  with  the  low  power  of  a  com- 
pound microscope. 

a.  What  is  the  nature  of  the  green  masses  observed  under 

a  low  power  ?  Are  they  composed  of  cells  ?  Do  you 
find  any  single  green  cells  ?  What  constitutes  a 
Protococcus  plant  ?  Is  it  unicellular  or  multicellular  ? 
Do  you  find  chloroplasts,  cell  wall,  etc.  ? 

b.  Sketch  two  or  three  green  masses  to  show  their  struc- 

ture as  you  observe  them.  Label  the  parts  in  terms 
of  cells  and  cell  structures. 

75 


76  LABORATORY  AND  FIELD  EXERCISES 

3.  Reproduction.    Study  the  method  of  reproduction  outlined 

and  illustrated  (Fig.  115)  for  Protococcus  in  the  text. 

a.  Observe  three  or  four  stages  in  reproduction  from  your 

mounts  of  Protococcus.  Is  this  a  vegetative  or  a 
sexual  method  of  reproduction  ?  Is  it  a  rapid  or  a 
slow  method  ?  What  becomes  of  the  loose  colonies 
formed  by  reproduction  when  the  plants  are  exposed 
on  bark,  boards,  or  stones  ? 

b.  Sketch  three  or  four  stages  in  the  reproduction  of  Pro- 

tococcus, beginning  with  a  single-celled  plant. 

4.  Dissemination.    How  does  Protococcus  spread  from  tree 

to  tree  or  from  any  one  habitat  to  another  ?  How  does 
it  form  a  large  incrustation  from  the  first  few  cells  in 
a  new  habitat  ?  Why  does  it  usually  occur  on  the 
north  side  of  trees  and  fences  ?  Why  is  it  more  abun- 
dant on  rough  than  011  smooth  surfaces  ? 

5.  Nutrition.    What  is  the  source  of  the  water,  gases,  and 

salts  which  constitute  the  raw  food  materials  for  Pro- 
tococcus plants  ?  How  are  these  materials  absorbed  ? 
Are  they  made  into  foods  and  used  by  Protococcus  as 
they  are  in  a  tree  or  a  geranium  plant?  Be  able  to 
indicate  the  income  and  outgo  of  food  materials  and 
wastes  in  Protococcus  plants. 

6.  Summary  and  discussion.    Discuss  briefly  in  your  notes 

the  mam  points  indicated  above  concerning  the  struc- 
ture, reproduction,  dissemination,  and  nutrition  of 
Protococcus. 

CHLA  MYDOMONA  S 

If  Chlamydomonas  is  available  for  study,  compare  it  with 
Protococcus  in  structure,  reproduction,  and  dissemination.  Note 
particularly  the  rate  and  mode  of  movements  in  active  Clilamy- 
domonas  plants.  The  brick-red  eyespot  and  the  cup-shaped 
chloroplast  may  be  observed  in  forms  which  have  come  to  rest. 


THE  PLANT  GROUPS  77 

SPIROGYRA  (WATER  SILK) 

1.  Habitat  and  habit.    Observe  plants  of  the  common  green 

scum  floating  in  an  aquarium  or  on  ponds  in  the  open. 
Eemove  a  small  portion  of  the  green  mass  to  a  watch 
glass.  Separate  somewhat  and  examine  with  a  hand 
lens  and  the  low  power  of  a  compound  microscope. 

a.  Is  the  green  mass  composed  of  one  plant  or  many  ? 

What  is  the  nature  of  the  Spirogyra  plant  ?  Has  it 
roots,  stems,  or  leaves?  How  does  it  differ  from 
plants  of  Protococcus  ? 

b.  Sketch  one  or  two  Spirogyra  plants  as  seen  under  a 

low  power.    Name  all  structures  observed. 

2.  Cell  structure.    Study  the  cells  of  a  Spirogyra  plant  under 

high  power.   Are  the  cells  composing  the  plant  all  alike 
or  are  they  differentiated  for  different  functions  ?   Note 
the  bandlike  chloroplasts.   How  many  are  there  in  each 
cell? 
a.  Chloroplast  and  pyrenoids.    Compare  fresh  and  stained 

plants  of  Spirogyra  in  the  study  of  the  pyrenoids. 

Read  the  text  concerning  the  structure  and  function 

of  the  pyrenoids. 

(1)  Stain  fresh  plants  with  iodine  solution  after  they 

have  been  exposed  to  sunlight.  Does  the  starch 
sheath  of  the  pyrenoid  contain  starch  ?  In  what 
part  of  the  pyrenoid  is  the  starch  stored  ? 

(2)  Compare   your   specimen  with   a   Spirogyra   plant 

which  has  been  specially  stained  and  mounted 
for  study.  Such  preparations  often  show  the 
pyrenoids  and  nucleus  with  great  distinctness. 

(3)  Sketch  a  portion  of  a  chloroplast  and  two  or  more 

pyrenoids  greatly  magnified.  Indicate  the  starch 
sheath  and  central  granule  of  the  pyrenoid  and 
the  form  and  structure  of  the  chloroplast. 


78  LABORATORY  AND  FIELD  EXERCISES 

b.  The  nucleus.  Study  the  nucleus  in  stained  material. 
What  is  the  form  of  the  nucleus  and  where  is  it 
located  in  the  cell  ?  Is  it  connected  with  the  pyre- 
noids  ?  Study  several  cells  with  reference  to  these 
points.  Draw  a  Spirogyra  cell  to  show  the  nucleus 
in  its  proper  position  and  in  its  connections  with 
the  pyreuoids.  Construct  a  transverse  section  of  a 
Spirogyra  cell  cut  through  the  nucleus.  Label  all 
parts  correctly.  See  Fig.  118  of  the  text. 
3.  Reproduction. 

a.  Conjugation  of  the  filaments. 

(1)  Study  early  conjugating  plants  with  a  low  power. 

Observe  the  method  of  union  of  the  filaments. 
Do  you  find  different  stages  in  the  formation  of 
protrusions  from  the  cells  and  in  the  formation 
of  connecting  tubes  ?  Observe  whether  the  union 
of  the  filaments  affects  the  cytoplasm  of  the 
uniting  parent  cells. 

(2)  Draw  stages  representing  the  union  and  conjugation 

of  the  filaments  in  Spirogyra. 

b.  Formation  of  the  gametes. 

(1)  Study  plants  in  which  gametes  are  forming.    Ob- 

serve as  many  stages  in  gamete  formation  as 
possible  in  the  material  at  your  disposal.  Do  you 
find  male  gametes  forming  before  the  female 
gametes  in  cells  united  by  connecting  tubes  ? 
What  is  the  method  of  gamete  formation  ?  What 
is  a  gametangium  ?  Consult  the  text  for  the 
meaning  of  this  term.  How  does  it  differ  from  a 
gamete  ?  What  are  the  structural  parts  of  each  ? 

(2)  Draw  gametangia  in  which  gametes  are  forming. 

Indicate  as  many  stages  in  gamete  formation  as 
you  find.  Label  gametangia  and  gametes. 


THE  PLANT  GROUPS  79 

c.  Fertilization. 

(1)  Observe  stages  in  which  gametes  are  fusing  to  form 

zygotes.  What  is  the  difference  in  the  behav- 
ior of  the  two  gametes  during  fertilization  ?  On 
what  basis  can  one  be  designated  as  male  and 
the  other  as  female  ? 

(2)  Draw  stages  in  fertilization  as  observed. 

d.  The  zygote. 

(1)  Study  cells  in  which  zygotes  are  formed.  What  is 
the  structure  of  the  zygote  cell  ?  Distinguish 
between  pyrenoids  and  nuclei  in  the  zygote  cell. 
Stain  zygotes  with  iodine.  What  kind  of  reserve 
food  does  the  zygote  contain  ?  When  and  for 
what  purpose  will  this  food  be  used  ?  Draw 
two  or  three  zygotes  to  illustrate  their  cell 
structure. 

4.  Life  history  of  Spirogyra  and  Protococcus.  Construct  a 
graphical  life  history  of  Spirogyra.  Is  it  possible  to 
construct  a  similar  graphical  history  for  Protococcus  ? 
In  what  fundamental  respects  does  the  life  history  of 
Spirogyra  differ  from  that  of  Protococcus  ? 

VMTHERIA   (GREEX  FELT) 

Select  fruiting  specimens  of  some  species  of  VaucJieria  for 
study.  Observe  the  following  points  regarding  its  habitat,  habit, 
and  structure : 

1.  Habit.  In  what  respect  is  Vaucheria  peculiar  in  its  gen- 
eral structure  ?  Is  it  a  simple  or  a  branched  filament  ? 
Is  the  plant  body  differentiated  into  root  and  shoot  ? 
What  is  its  general  microscopic  structure  ?  Is  it  uni- 
cellular or  multicellular  ?  What  kind  of  chloroplasts 
has  it? 


80  LABORATORY  AND  FIELD  EXERCISES 

2.  Sexual  reproduction.    Mount  fruiting  plants  of  Vauelieria 

after  teasing  them  apart  with  dissecting  needles  in  a 
drop  of  water.  Search  for  reproductive  branches  with 
a  low  power. 

a.  Female  gameiangia  and  gametes.    Search   for  greatly 

swollen  and  shortened  lateral  branches  representing 
the  female  gametangia. 

(1)  Do  these  reproductive  branches  differ  from  the  ordi- 

nary branches  of  the  plant  body  except  in  size  ? 
What  is  the  nature  of  the  protoplast  and  of 
the  embedded  chloroplasts  in  these  reproductive 
branches  ?  Do  you  find  a  projecting  beak,  or  ros- 
trum, at  one  side  of  the  reproductive  branch  ?  It 
is  at  this  point  that  the  cell  wall  of  the  game- 
tangium  breaks  down  and  allows  the  male  gamete 
to  enter  the  egg. 

(2)  In  properly  prepared  material  the  nature   of  the 

protoplast  and  the  location  of  the  chloroplast  and 
•nucleus  may  be  seen.  Observe  carefully  with  the 
high  power. 

b.  Male  gametangium.    The  male  gametangium  is  usually 

represented   by   a   curved   branch  near  the  female 
gametangium. 

(1)  Note  the    nature    of   the    protoplast    of   the    male 

gametangium.  Contrast  it  with  that  of  the 
female.  Male  gametes  cannot  usually  be  found 
in  VaucJieria.  If  they  have  been  expelled,  the 
gametangium  looks  light-colored  and  empty. 

(2)  Draw  a  portion  of  a  plant  bearing  male  and  female 

gametangia.    Detail  the  female  gametes. 

3.  Vegetative  and  asexual  reproduction.  Vegetative  reproduc- 

tion occurs  in  Vauclieria  by  means  of  nonmotile  repro- 
ductive branches  which  are  merely  swollen,  club-shaped 


THE  PLANT  GROUPS  81 

lateral  branches,  bright  green  in  color.  Motile,  free- 
swimmiug  spores  or  zoospores  are  also  formed  in  some 
species  as  asexual  bodies. 

a.  Vegetative  reproduction.     Search   for  the    club-shaped 

branches  with  a  low  power.  How  are  they  formed  ? 
How  do  they  become  free  from  the  mother  plant? 
How  would  they  grow  into  a  new  Vaucheria  plant  ? 
Do  you  find  free  productive  branches  in  your  material? 

b.  Asexual  reproduction  by  zoospores.    These  are  difficult 

to  demonstrate   in    Vaucheria  except   in  unusually 
favorable  material.  Draw  any  stages  of  asexual  repro- 
duction which  you  have  succeeded  in  demonstrating. 
4.  Life  history.    Write  a  graphical  life  history  of  Vaucheria 
similar  to  that    constructed  for  Spirogyra.    In  what 
respect  are  the  two  life  histories  similar  ?    In  what  re- 
spects different  ?    Which  alga  has  the  higher  type  of 
reproductive  process  ?   Explain.    What  is  the  function 
of  vegetative  and  asexual  reproduction  as  contrasted 
with  sexual  reproduction  in  a  plant  like  Vaucheria  ? 


(EDOGONIUM 

Habit.  Study  plants  of  (Edogonium  and  compare  them 
with  ftpirogyra  and  Vaucheria  as  regards  form  and 
structure.  How  do  the  cells  differ  in  form  and  contents 
from  the  other  algte  studied  ?  Draw  a  plant  of  (Edo- 
gonium  to  illustrate  its  habit  and  cell  structure. 
Reproduction.  Study  plants  in  which  the  gametes  are 

forming. 

a.  Female  gametangia  and  gametes.  Observe  one  or  two 
stages  in  the  formation  of  female  gametes  from  single 
cells  of  the  filament  as  described  in  the  text.  How 
is  the  female  gamete  formed  ?  What  is  its  structure  ? 


82  LABORATORY  AND  FIELD  EXERCISES 

Sketch  one  or  two  stages  in  the  formation  of  female 
gametes.  Label  accurately. 

b.  Male  gametangia  and  gametes.    If  material  is  available, 

study  the  male  gametangia  and  gametes  as  described 
and  figured  in  the  text.  Sketch  stages  demonstrated, 
and  label. 

c.  The  zygote.    Study   the   zygote   of    (Edogonium.    Is  it 

adapted,  by  its  cell  structure,  for  carrying  the  plant 
over  an  inclement  period  ?  Note  its  form  and  con- 
tents. Draw. 

d.  Asexual  reproduction.    The  asexual  reproductive  process 

is  difficult  to  demonstrate  with  beginning  classes  and 
should  be  studied  from  the  text  and  figures. 

e.  Life  history.    Write  a  graphical  life  history  of  (Edogo- 

nium similar  to  that  outlined  for  Spirogyra.  How  is 
this  history  adapted  to  seasonal  changes  ? 

GENERAL  STUDY  OF  FRESH-WATER  ALG.E 

1.  Examine   water    containing    free-floating    algae,   or   algse 

attached  to  objects  covered  by  water.  If  algse  are 
scraped  from  surfaces,  they  should  usually  be  separated 
on  the  slide  with  needles  or  by  gently  tapping  the 
cover  glass  with  needles.  Mount  in  fresh  water  and 
examine  first  with  low  power. 

2.  Form  and  structure.    Note  the  number  and  kinds  of  algte 

living  together  in  one  place.  How  many  distinct  kinds 
or  species  of  algre  can  you  distinguish  in  the  water  you 
are  examining  ?  Are  there  unicellular  forms  ?  many- 
celled  forms  ?  Have  any  species  the  power  of  movement? 
Note  differences  in  the  form  or  color  of  the  chloroplasts 
in  different  species. 

3.  Reproduction.    Are  any  of  the  species  that  you  are  ex- 

amining reproducing  either  vegetatively,  asexually,  or 


THE  PLANT  GKOUPS  83 

sexually  ?  If  so,  trace  out  the  stages  of  reproduction 
found  in  your  material. 

4.  Sketch  the  different  species  of  algse  observed  and  show 
stages  in  reproduction  where  such  are  observed. 

FUCUS   VESICULOSUS  (MARINE  ALGA) 

1.  Habitat  and  habit. 

a.  Is  the  water  habitat  of  Fucus  more  or  less  stable  and 
permanent  than  that  of  fresh-water  algse  ?  Do  you 
know  of  fresh-water  forms  which  attain  to  the  size 
or  the  structural  differentiation  of  Fucus  ?  Is  there 
a  reason,  based  on  difference  of  habitat,  for  this 
difference  in  habit  between  Fucus  and  fresh-water 
species  ?  Note  the  differentiation  of  the  plant  body  into 
root  and  shoot  portions.  What  is  the  function  of  the 
root  and  shoot?  How  is  each  part  adapted  to  its 
special  function  ?  How  is  it  adapted  to  photosyn- 
thesis ?  to  resistance  to  waves  and  water  currents  ?  to 
protection  from  dessication,  or  drying,  when  exposed 
at  low  tide  ? 

I.  Study  the  form  and  branching  of  Fucus.  Can  you  de- 
termine how  the  very  regular  mode  of  branching 
occurs  ?  Where  are  the  growing  points  ?  Is  there  any- 
thing like  a  bud  ?  Observe  the  swollen  floats  which 
buoy  the  plant  up  in  water. 

c.  Sketch  a  portion  of  a  Fucus  plant  to  show  its  habit  and 
mode  of  branching. 

2.  Microscopic  structure.    Examine  thin  sections  cut  across 

a  FufMS  plant.  What  is  its  general  structure  ?  Is  there 
an  outer  protective  epidermis  ?  Where  is  the  chlorophyll 
layer  or  layers?  Does  the  chlorophyll-bearing  layer 
look  green?  Explain  the  color  of  this  layer.  What 
kind  of  tissue  occupies  the  center  of  the  branch  as 


84  LABORATORY  AND  FIELD  EXERCISES 

shown  in  the  section  ?  Is  Fucus  composed  of  a  true 
cellular  tissue  like  a  geranium  ?  Make  an  outline 
drawing  of  the  section,  shading  in  the  chlorophyll- 
bearing  layer.  Detail  a  few  cells  of  each  layer  to 
show  the  cellular  structure. 
3.  Reproduction. 

a.  Reproductive  branches.    Eead  the  text  description  of 

reproduction  in  Fucus. 

(1)  How  are  the  reproductive  branches  distinguishable 

from  the  ordinary  vegetative  branch  tips  ?  Find 
the  male  reproductive  branches,  covered  with  a 
yellow  exudation  of  slime  containing  the  male 
gametes.  Learn  to  recognize  the  female  branches 
by  the  greenish  exudation  of  slime  containing 
female  gametangia. 

(2)  Ostia,  or  pores.    Observe  ostia  with  a  hand  lens  on 

the  surface  of  the  reproductive  branches  or  with 
a  low  power  in  thin  horizontal  surface  sections  of 
reproductive  branches. 

b.  Crametes  and  gametangia  (living  material). 

(1)  Male  gametangia  and  gametes.    Touch  the  surface 

of  a  slide  with  male  branches  which  are  exuding 
yellow  slime.  Mount  and  observe  the  saclike 
male  gametangia  containing  male  gametes,  which 
look  like  yellow  dots.  Look  for  male  gametes 
free  from  the  gametangia  on  the  slide.  Can  you 
distinguish  the  movement  of  these  male  gametes  ? 
their  form  and  structure  ?  A  brick-red  spot,  "  the 
eyespot,"  is  usually  visible. 

(2)  Draw    male   gametangia   and    gametes    somewhat 

magnified. 

(3)  Female  gametangia  and  gametes.    These    may   be 

obtained  as  in  the  case  of  the  male  gametes.    Note 


THE  PLANT  GROUPS  85 

the  saclike  gametangia  inclosing  from  four  to  six 
visible  divisions  of  the  contained  protoplast.  These 
are  the  future  gametes.  Search  for  other  speci- 
mens in  which  eight  eggs,  or  female  gametes,  are 
rounded  up  inside  of  the  gametangium  membrane. 
Find  also  free  eggs  which  have  been  liberated,  as 
they  are  in  nature,  from  the  gametangium.  What 
is  the  structure  of  the  female  gamete  ?  How  does 
it  compare  in  size  with  the  male  gamete  ?  Is  the 
female  gamete  motile  ?  What  advantage  is  there 
in  the  small  male  gametes  and  the  large  female 
gamete  ?  Draw  a  gametangium  containing  devel- 
oping gametes  and  a  free  female  gamete. 

c.  Fertilization.     The  swarming  of  gametes  around  the 

eggs  may  often  be  observed  if  the  two  gametes  are 
mounted  together  in  sea  water.  The  act  of  fertiliza- 
tion is  too  difficult  for  observation  by  the  beginner. 

d.  Female   gametangia    and  gametes.    Observe    prepared 

sections  cut  through  female  receptacles  and  stained. 
Note  the  flask-shaped  receptacles  from  the  wTalls  of 
which  the  oogonia  and  paraphyses  grow  out  into  the 
cavity  of  the  conceptacle.  Study  different  stages  in 
the  formation  of  the  female  gametangia  and  gametes. 
Do  you  find  small  gametangia  with  a  single  nucleus 
and  cytoplasm  ?  Search  for  other  stages  in  which 
there  are  many  nuclei.  Find  stages  in  which  cell 
walls  have  been  formed  separating  the  cytoplasm  of 
the  oogonium  into  eight  gametes.  Draw  the  stages 
of  the  gametangium  observed,  illustrating  different 
stages  in  the  formation  of  gametes. 

e.  Male  gametangia   and  gametes.    Observe  sections   cut 

through  male  reproductive  branches  of  Fucm.  Are 
the  gametes  visible  within  the  gametangia  ?  How  do 


I  LABORATORY  AND  FIELD  EXERCISES 

they  compare  in  number  and  size  with  the  female 
gametes  ?    Were  the  male  gametes  formed  like  the 
females,  by  cell  and  nuclear  division  ?   Draw. 
/.  Life  history.    Write  a  graphical  life  history  of  Fucus 
similar  to  that  of  tipirogyra  and  Vaucheria. 

B.  THE  FUNGI 
YEAST 

1.  Composition  of  compressed  yeast. 

a.  Method.    Remove  a  small  portion  of  compressed  yeast 

to  a  slide  and  mount  in  a  drop  of  water,  separating 
well  with  needles.  Add  weak  iodine  solution  and 
observe  with  low  and  high  powers  of  the  microscope. 

b.  Observation.   Do  you  find  indications  of  the  presence  of 

starch  in  yeast  cakes  ?  Can  you  distinguish  the  minute 
yeast  plants  looking  like  dots  under  low  power  ?  Ex- 
amine these  structures  with  a  high  power.  What  is  the 
structure  of  a  yeast  plant  ?  Contrast  it  with  an  alga 
like  Protococcus.  In  what  respects  are  the  two  plants 
similar  ?  In  what  respects  are  they  different  ?  Why 
is  the  yeast  cake  not  made  up  from  pure  yeast  plants  ? 

c.  Make  a  drawing  to  indicate  the  composition  of  com- 

pressed yeast. 

2.  Cellular  structure. 

a.  Method.  Cultivate  yeast  by  adding  about  1  g.  of  com- 
pressed yeast  cake  to  15  cc.  of  a  sugar  solution  made 
up  as  follows :  to  1 0  0  cc.  of  water  add  2  0  cc.  of  com  m  on 
molasses,  or  make  up  a  10-15  per  cent  sugar  solution 
in  water.  Keep  the  sugar  solution  at  about  25°-28°  C. 
after  adding  the  yeast  in  the  above  proportions.  After 
vigorous  growth  and  fermentation  have  begun,  add  a 
drop  of  the  solution  to  a  glass  slide  and  cover. 


THE  PLAisT  GKOUPS 


87 


b.  Structure  of  the  growing  yeast  plant. 

(1)  Study  a  mount  of  the  above  yeast  solution  with  low 
and  with  high  powers  of  the  microscope.  Is  the 
yeast  plant  unicellular  or  is  it  composed  of  more 
than  one  cell  ?  Are  all  the  yeast  plants  on  the 
slide  the  same  in  size  and  in  cellular  structure  ? 


0  |   &  6 


0 


FIG.  20.    Various  kinds  of  wine  and  beer  yeasts 

o,  fo,  wine  yeast  (S.  ellipsoideus)  (a,  young  and  vigorous;  b,  old  (1)  and  dead  (2)) ; 
c,  d,  beer  yeast  (S.  cerevisise)  (c,  bottom  yeast;  d,  top  yeast).   After  Marshall 

(2)  Select  a  large   unicellular   plant   and   observe   its 

minute  structure.  Is  the  yeast  cell  like  a  root- 
tip  cell  ?  How  does  it  differ  from  the  cell  of  an 
alga  like  Protococcus  ?  What  fundamental  nutri- 
tive process,  performed  by  Protococcus,  is  impos- 
sible for  yeast  plants  ?  Draw  and  name  the  parts 
of  a  large  yeast  cell. 

(3)  How  do  the  small  yeast  cells  differ  from  the  large 

cells  in  structure  ?  Draw  a  small  yeast  cell  and 
compare  with  the  large  cell  drawn  above. 


!  LABORATORY  AND  FIELD  EXERCISES 

3.  Reproduction  by  budding. 

a.  Do  you  find  yeast  plants  with  two  cells  joined,  namely, 
one  large  cell  united  with  a  small  cell  ?  Observe  a 
number  of  these  cases  of  two-celled  or  three-celled 
plants.  Are  the  two  or  three  united  cells  always 
unlike  in  size  ?  Can  you  determine  how  these  united 
cells  originate  from  single-celled  plants  ? 

6.  Draw  a  series  of  two-celled  yeast  plants  representing 
differences  in  size  between  the  constituent  cells. 
Can  you  now  determine  the  methqjl  by  which  the 
yeast  plant  reproduces  itself  by  budding  ?  How  does 
this  method  of  reproduction  differ  from  that  found 
in  Protococcus  ?  Is  it  a  sexual  or  a  vegetative  method 
of  reproduction? 

c.  Observe,  if  possible,  wild  yeasts  in  cider  or  in  ferment- 
ing apples  and  make  drawings  to  sho\v  their  struc- 
ture and  mode  of  reproduction. 

4.  Fermentation  experiments.   Select  two  flasks  of  equal  size 

and  into  one  pour  enough  water  to  cover  the  bottom. 
Into  the  other  flask  pour  an  equal  amount  of  actively 
fermenting  yeast  solution. 

a.  Test  both  flasks  for  oxygen  and  carbon  dioxide  with  a 

flame,  with  lirnewater,  or  with  bariiun  hydroxide. 
Set  aside  for  an  hour,  keeping  both  flasks  at  a  uni- 
form temperature  of  25°  C.  At  the  end  of  an  hour 
test  as  above  for  oxygen  and  carbon  dioxide.  Result  ? 

b.  Write  up  the  above  experiment  in  your  notes,  indicat- 

ing the  object,  the  actual  results  observed,  and  your 
conclusions  concerning  what  was  proved  with  refer- 
ence to  the  nature  of  fermentation  by  yeast.  See 
account  of  fermentation  in  the  text. 

c.  Fill  two  fermentation-  tubes  with  yeast  solution.    Keep 

one  at   25°  C.   and    the    other    at    a    much    lower 


THE  PLAXT  GROUPS  89 

temperature.  Observe  the  two  tubes  every  fifteen 
minutes  or  at  such,  intervals  as  you  find  necessary. 
Eesults  ?  How  do  you  explain  the  differences  ob- 
served in  the  two  tubes  ?  At  the  end  of  an  hour 
test  the  two  tubes  for  carbon  dioxide.  Eesult? 
Write  up  the  above  experiment  in  terms  of  object, 
method,  results,  and  conclusions  to  be  drawn  con- 
cerning the  nature  of  fermentation.  Indicate  method 
and  results  by  drawings. 

5.  Nutrition.  Draw  a  diagram  of  a  yeast  plant  greatly  mag- 
nified. Indicate  the  income  and  outgo  of  the  yeast  cell, 
comparing  its  nutritive  processes  with  those  of  Proto- 
coccus  and  a  specialized  green  plant.  Contrast  briefly 
the  nutrition  of  yeast  and  that  of  green  plants  like 
Protococcus  and  Geranium  (see  Fig.  2  of  the  text). 

BACTERIA 

CLASS  EXPERIMENTS 

1.  Expose  a  sterilized  culture  dish  containing  nutrient  gelatine, 
agar-agar,  or  other  suitable  substance  for  bacterial  growth 
in  the  classroom  or  laboratory  for  fifteen  or  twenty 
minutes.    Expose  a  second  culture  dish  out  of  doors  or 
in  a  quiet  room.    Cover  and  observe  after  the  cultures 
have  remained  for  twenty-four  hours  in  a  warm  place. 
a.  Are  there  colonies  of  bacteria  formed  on  the  culture 
media  in  both  cultures  ?   Is  there  any  difference  in 
the  number  and  kinds  of  colonies  in  the  two  dishes  ? 
How  do  you  account  for  any  differences  observed  ? 
b.  Study  the  colonies  with  a  hand  lens  or  with  a  low 
power  of  a  compound  microscope.    Are  there  differ- 
ences  in   the   size,  form,  or   color   of   the   different 
colonies?    Can  you  account  for  such  differences? 


90  LABORATORY  AND  FIELD  EXERCISES 

c.  Draw  the  colonies  of  one  culture  dish,  indicating  their 

distribution,  size,  and  form. 

d.  Conclusions.    State    your    conclusions    concerning    the 

following  points : 

(1)  How  do  you  account  for  the  difference  in  the  growth 

of  bacterial  colonies  in  the  two  culture   dishes 
exposed  to  the  air  in  the  two  different  situations  ? 

(2)  How  are  bacteria  evidently  distributed?  "Why  should 

one   avoid    crowded   rooms   in  time    of   disease 
epidemics  ? 

(3)  How  do  you  account   for  the  differences  in   the 

appearance  of  different  bacterial  colonies  ? 
2.  Expose  a  sterile  liquid  culture  medium  in  a  test  tube  to 
the  air  as  in  the  first  experiment.    Observe  for  several 
days  at  successive  class  exercises.    Note  any  changes 
in  the  fluid  which  appear  from  day  to  day. 

MICROSCOPICAL  EXAMINATION  OF  BACTEKIA 

1.  Remove  a  small  portion  of  a  colony  from  one  of  the  cul- 

ture dishes  in  experiment  1  to  a  drop  of  water  on  a 
glass  slide  and  cover. 

2.  Prepare    a    similar    slide    from    the    liquid    culture    in 

experiment  2. 

3.  Observe  these  preparations  first  with  a  low  power  and 

then  under  the  high  power  of  a  compound  microscope. 

a.  Form  types  of  bacteria.  Consult  the  text  figures  and 
discussions  and  observe  as  many  of  these  forms  of 
bacteria  as  you  can  find  in  your  preparations.  Do  you 
find  coccus,  bacillus,  and  spirilla  form  types  ?  Note 
the  great  variation  in  form  and  size  of  the  bacteria, 

I.  M<»'<-iin'iitx.  Do  you  find  bacteria  with  independent 
powers  of  movement?.  What  is  the  nature  of  this 
movement  ?  The  motor  organs,  cilia  or  tiagella,  can 


TILE  PLANT  GROUPS 


91 


only  be  seen  with  very  high  powers  in  stained  prepara- 
tions. Omit  unless  such  preparations  are  available. 
c.  Cell  division.  Do  you  see  any  bacteria  in  which  the 
cells  are  dividing  ?  Consult  Fig.  135  of  the  text,  and 
the  discussion  on  vegetative  reproduction  in  bacteria. 


Fi<;.  21.    Form  types  of  bacteria 

typ»s  of  bacilli;  b,  types  of  micrococci;  c,  types  of  spirilla.    After  Williams 
From  Marshall's  "  Microbiology  " 

d.  If    stained    preparations    of    bacteria    are    available, 

study  the  structure  and  form  of  bacteria  in  such 
preparations. 

e.  Drfi"'ti/</x.    Draw  the  form  types  of  bacteria  observed. 
f.  Bai'li'r'ia  »f  l]i<-  //r///.    Scrape  the  teeth  with  a  sterilized 

needle,  or  scalpel.  Sterili/e  first  in  a  flnme  or  in 
strong  alcohol.  Mount  and  observe.  Do  you  find 
more  than  one  form  of  bacterial  cell  in  your  prepa- 
ration? How  many  do  you  find?  Make  a  drawing 
of  the  bacteria  found  on  the  teeth. 


92  LABOKATOKY  AND  FIELD  EXERCISES 

MOLDS 
GENERAL  NATURE  OF  MOLDS 

Examine  molds  growing  on  various  substances  in  the  labora- 
tory and  note  the  following  points  regarding  their  habitat,  habit, 
and  general  structure : 

1.  Habitat.    Upon  what  kinds  of  substances  do  molds  grow  ? 

Are  these  substances  sweet  or  sour  ?  acid  or  alkaline  ? 
solid  or  liquid  ?  How  would  the  income  and  outgo  of 
molds  in  the  form  of  gases,  liquids,  and  solids  compare 
with  that  of  a  green  plant  like  Protococcus  or  a  Gera- 
nium ?  Do  molds  differ  in  the  above  particulars  ?  Com- 
pare the  income  and  outgo  of  a  mold  on  bread  with 
that  of  yeast  and  Protococcus.  Be  able  to  point  out 
similarities  and  differences  in  the  habitats,  and  in  the 
substances  derived  from  them,  in  the  three  cases  cited. 

2.  Habit.    Is  a  mold  plant  on  bread  or  apples  differentiated 

into  organs  or  tissues  like  a  higher  plant  ?  See  Figs.  139 
and  140  of  the  text.  Do  different  species  of  molds  show 
differences  in  color  or  structure  ?  To  what  great  group 
of  green  plants  are  molds  most  nearly  related  in  their 
general  structure  and  differentiation  ?  In  what  impor- 
tant respect  do  they  differ  from  this  plant  group  ? 

3.  Gross  structure  and  growth. 

a.  G-rowth  (use  hand  lens).    Examine  patches  of  mold  on 

apples,  bread,  and  other  media  with  naked  eye  and 
hand  lens.  Do  the  patches  of  mold  observed  seem  to 
have  any  definite  method  of  .spreading  by  growth  ? 
Can  you  account  for  the  circular  appearance  (Fig.  143 
of  text)  often  observed  in  patches  of  mold  ?  Are  some 
patches  colored  ?  Where  is  the  colored  portion  ? 

b.  Eemove  some  of  the  colored  and  colorless  portions  of 

different  kinds  of  molds  to  different  slides  and  mount 


THE  PLANT  GROUPS  93 

the  material  from  each  mold  separately  in  water  or 
in  a  mixture  of  alcohol  and  glycerin.  Study  the 
structures  found  in  the  colored  and  colorless  portions 
of  your  mounts.  What  do  you  conclude  as  to  the 
nature  and  function  of  these  colored  and  colorless 
portions  of  molds  ?  Are  all  molds  which  you  examine 
alike  in  the  general  structure  of  colored  and  colorless 
parts  ? 

c.  Draw  diagrams  to  illustrate  the  structures  found  in  the 
colored  and  colorless  parts  of  various  molds.  See  text 
and  figures  on  black  and  blue-green  molds. 

4.  Nutrition  of  molds  (for  example,  apple  mold). 

a.  Method.     Remove  some  of  the  pulp  from  a  decaying 

apple  with  needles  or  the  point  of  a  scalpel  and 
place  on  the  center  of  a  glass  slide.  Add  eosin  solu- 
tion and  crush  out  gently  under  a  cover  glass.  The 
mold  filaments,  if  present  in  the  apple,  will  stain  red 
with  eosin. 

b.  Observation.    Do    you    find    mold    filaments    (hyphse) 

among  the  apple  cells  ?  What  is  their  function  ?  their 
structure  ?  How  are  they  related  to  the  white  aerial 
mycelium  and  to  the  colored  spores  on  the  outside  of 
the  apple  ?  Into  what  parts  is  the  body  of  the  apple 
mold  divided  ?  What  is  the  functional  relation  of  these 
parts  ?  What  kind  of  food  would  the  mold  secure 
from  apples  ?  How  would  it  absorb  it  ?  Compare  the 
income  and  outgo  of  apple  mold  with  that  of  the  wild 
yeasts  in  apple  or  in  cider.  Draw  a  portion  of  the 
apple  mold  as  it  appears  within  the  apple.  Include 
the  cells  of  the  apple  pulp  surrounding  the  hyphae. 

5.  Summarize  briefly  the  distinctive  characteristics  of  molds 

observed  under  the  above  topics,  namely,  Habitat,  Habit, 
Gross  Structure  and  Growth,  and  Nutrition. 


94  LABORATORY  AND  FIKLD   EXERCISES 

SPECIAL  STUDIES  OF  MOLDS 

RmZOPUS  NlGRICANS  (BLACK  MOLD) 

THE  MYCELIUM  AND  NUTRITION 

1.  Spores  and  spore  germination.    Study  spores  which  have 

been  growing  on  prune  juice  or  some  other  nutrient 

medium  for   different  lengths  of  time ;    for   example, 

twenty-four,  forty-eight,  and  seventy-two-hour  periods. 

a.  Early  stages  in  spore  germination.    Use  cultures  which 

have   been   grown    from    twenty-four   to    thirty-six 

hours  at  25°  C. 

(1)  What  is  the  earliest  stage  of  spore  germination  that 

you  can  find  ?  What  change  takes  place  in  the 
form  and  structure  of  a  spore  when  it  begins  to 
germinate?  Does  the  entire  spore  cell  elongate, 
or  only  certain  portions  of  it,  to  form  the  begin- 
ning of  a  hypa  or  mold  filament  ?  Do  you  find 
branched  hyplue  growing  from  spores  ?  Note  the 
structure  of  the  longer  hyplue,  including  details 
of  cellular  structure.  Are  there  vacuoles  ?  Is 
there  a  cytoplasmic  sac  or  is  there  solid  cyto- 
plasm in  the  young  hyphse  ?  (The  nuclei  of 
KhizopuM  cannot  be  seen  in  fresh  material.)  Is  the 
hypha  produced  by  spore  germination  unicellular 
or  rnulticellular  ? 

(2)  Draw  two  or  three  stages  in  spore  germination,  to 

show  the  spore,  the  progressive  growth  of  a 
hypha  from  a  spore,  and  the  cellular  structure  of 
the  hyphal  cell. 

2.  Development   of    the    mycelium.    Study  later   stages    in 

spore  germination  from  cultures  which  have  grown  for 
forty-eight  and  seventy-two  hours. 


PLANT  GROUPS  95 

a.  Note  the  changes  in  the  hyphpp  produced  after  a  longer 

period  of  growth.  Are  they  branched  or  unbranched  ? 
unicellular  or  inulticellular  ?  Have  they  the  same 
structure  as  in  the  earlier  stages  noted  above  ?  Is 
the  spore  still  visible  ?  Draw  two  or  three  of  these 
older  stages  in  spore  germination.  Label  correctly. 

b.  Observe  the  mycelium  of  Jthizopus  growing  on  bread  or 

some  other  medium.    How  was  this  mycelium  pro- 
duced ?    How  related  to  the  branched  hyphse  noted 
above  as  a  result  of  spore  germination  ?    How  do  you 
account  for  the  origin  of  a  mycelium  on  moist  bread 
or  in  a  moist  chamber  upon  which  no  spores  are 
artificially  sown  ?    Is  there  a  submerged  mycelium 
within  the  nutrient  medium  and  an  aerial  portion 
exposed  to  the  air  ?   What  is  the  function  of  the  two 
parts  of  the  mycelium?    See  text  and  Fig.  140. 
3.  Nutrition.    How  does  RJiizopus  differ  from  apple  mold  in 
the  nature  of  its  habitat  ?   Are  the  foods  of  its  habitat 
solid  or  liquid  ?    In  the  case  of  Rhizopus  growing  on 
bread,  how  does  the  fungus  absorb  and  use  the  starch 
of  the  bread  as  food  ?    Contrast  the  nutrition  of  the 
apple  mold  and  that  of  Khizopu*  growing  on  bread. 

REPRODUCTION 

1.  Spore  formation  by  sporangia.  Observe  a  mycelium  upon 
which  round  balls,  or  sporangia,  begin  to  appear  (Fig.  139 
of  text).  Place  a  patch  of  this  mycelium  with  light- 
colored  sporangia  on  a  slide  and  observe  with  a  low 
power  without  mounting. 

a.  What  is  the  relation  of  the  sporangia  to  the  hyphse  ? 
How  are  the  sporangia  related  to  the  hyphte  of  the 
mycelium  ?  Are  they  formed  by  any  special  hyphal 
branches  ?  Consult  the  text  and  Fig.  140. 


96  LABORATORY  AND  FIELD*  EXERCISES 

b.  Mount  the  above  specimen  in  glycerin  and  alcohol  and 

determine  the  relation  of  the  sporangia  to  the  hyphte. 
What  is  the  structure  of  a  sporangial  head  ?  What 
is  the  nature  of  the  contents  of  the  young,  light-colored 
sporangia  ?  Consult  Fig.  141  of  text. 

c.  Bead -the  text  011  asexual  reproduction  and  spore  forma- 

tion in  Rhizopus.  Demonstrate  as  many  of  the  stages 
of  spore  formation  described  in  the  text  as  you  can. 

d.  Draw  at  least  two  stages  of  young,  light-colored  sporan- 

gia, including  one  in  which  spores  are  being  formed. 

2.  Mature  sporangia  and  spores.   Study  mature  sporangia  and 

note  the  columella,  the  sporangium  wall,  and  the  spores. 
What  is  the  color  and  structure  of  the  liypha  which  bears 
mature  sporangia  ?  Do  you  find  the  stolons  and  rootlike 
hyphse  connected  with  the  liypha  which  bears  the  sporan- 
gium ?  See  the  text  under  Habit  of  Eliizopus.  Draw 
a  mature  sporangium  and  show  its  connection  with 
the  main  mycelium.  Indicate  stolons  and  rootlike  out- 
growths at  the  base  of  a  sporangium-bearing  liypha. 

3.  Sexual  reproduction.    B  material  is  available,  demonstrate 

stages  in  the  sexual  process  of  Rliizopus.  Read  the  text 
on  sexual  reproduction.  Demonstrate  suspensors,  game- 
tangia,  and  zygotes,  if  seen  in  your  material.  Draw 
stages  observed  in  sexual  reproduction.  Label  correctly. 

4.  Life  history.    Write  a  graphical  life  history  of  Rliizopus 

similar  to  that  already  outlined  for  Spirogyra  and  other 
green  plants. 

PENICILLIUM  AND  ASPERGILLUS 

1.  Habitat  and  habit.     See   the  general  nature  of   molds 

previously  studied. 

2.  Mycelium  structure.    Remove  small  portions  of  the  myce- 

lium of  a  blue  mold,  mount,  and  study.  Has  it  the  same 


THE  PLANT  GEOUPS  97 

structure  as  that  of  Rhizopus  ?  Is  it  unicellular  or  multi- 
cellular  ?  Note  the  structure  of  the  hyphse.  Draw  a 
small  portion  of  the  mycelium  of  a  blue  mold,  to  differ- 
entiate it  from  the  mycelium  of  Rhizopus.  Label 
correctly. 

3.  Spore  production.    Eead  the  description  of  spore  formation 

in  PenieUlium  and  Asperyillus  (Figs.  144  and  145)  in 
the  text.  Observe  spore-bearing  cultures  of  these  molds 
as  for  Rhizopus.  How  do  these  molds  differ  from 
Rhizopus  in  their  method  of  spore  formation  ?  How 
does  Penidllium  differ  from  Aspergillus  in  this  respect  ? 

4.  Draw  appropriate  diagrams  to  express  the  methods   of 

spore  formation  in  Penicillium  or  Aspergillus.  State 
concisely  the  difference  in  the  method  of  spore  forma- 
tion in  RkizopuB  and  the  blue  molds. 

MUSHROOMS   AND  THEIR  ALLIES 

MUSHROOMS 

1.  Habitat.    What  is  the  habitat  of  mushrooms  ?    Be  able  to 

name  a  number  of  habitats  for  mushrooms  and  their 
allies,  the  bracket  fungi.  What  forms  a  common 
ingredient,  or  component,  of  the  soil  in  all  mushroom 
habitats  ? 

2.  Habit  and  parts. 

a.  What  are  the  parts  of  a  common  mushroom  ?  What 
are  the  submerged  portions  in  the  soil,  log,  or  other 
mushroom  habitat  ?  See  complete  specimens  for  this, 
including  subterranean  parts.  What  is  the  general 
form,  texture,  and  color  of  the  aerial  parts  ?  Observe 
the  underside  of  the  umbrellalike  aerial  portion. 
What  do  you  find  ?  What  is  the  function  of  these 
structures  on  the  underside  of  the  umbrella  ? 


98  LABORATORY  AND  FIELD  KXKKCISKS 

b.  Examine  mushrooms  of  different  ages.    Is  the  color  of 

these  plates,  or  gills,  the  same  in  young  anil  in  old 
specimens  ?  Compare  the  color  change  which  you 
observe  with  that  of  molds.  What  is  the  function  or 
use  of  the  plates,  or  gills  ? 

c.  Bisect  a  mushroom  vertically  through  the  umbrella  and 

its  stalk.  Study  the  relation  of  the  gills  to  the  umbrella. 
Draw  the  cut  surface  of  the  mushroom  and  include  the 
subterranean  and  the  aerial  parts.  (The  subterranean 
portions  may  be  drawn  from  specially  prepared  material 
if  they  are  not  available  in  the  laboratory  specimens.) 
liead  the  paragraph  in  the  text  and  consult  Fig.  147 
on  the  parts  of  the  mushroom.  Label  correctly  the 
parts  of  your  figure  showing  the  habit  of  the  muslin  >om. 

3.  Nutrition.    State  concisely  the  function  of  each  part  of 

the  mushroom  drawn  above.  Indicate  the  income  and 
the  outgo  of  the  mushroom  in  gases,  liquids,  and  soh'ds 
in  connection  with  the  above  figure  or  in  an  outline 
figure  similar  to  Fig.  2,  Part  I,  of  text. 

4.  Growth  and  expansion  of  mushrooms.    Study  a  series  of 

mushrooms  of  different  ages.  "What  changes  in  the 
size,  form,  and  relation  of  parts  do  you  find  taking  place 
in  mushrooms  from  young  to  mature  stages  \  What  is 
the  apparent  function,  or  use,  of  these  changes  ?  Praw 
a  series  of  diagrams  to  illustrate  the  growth  stages  of 
a  mushroom  and  discuss  briefly  the  function,  or  use, 
of  the  changes  indicated  by  your  drawings. 

5.  Structure.    Tease  out  on  a  slide  portions  of  the  stipe  of  a 

mushroom.  Mount  and  study.  Is  the  mushroom  cel- 
lular like  a  higher  plant,  or  is  it  an  aggregation  of 
hypha'  ?  Contrast  the  structure  of  a  mushroom  and 
that  of  a  mold.  Make  drawings  to  indicate  the  structural 
elements  of  the  mushroom. 


TJIE  PLANT  (JliOri'S  99 

6.  Spore  formation.    Select  spore-forming  lamellae  of  some 

species  of  Coprinus.  Peel  off  a  small  portion  of  the 
s]  lore-bearing  surface  and  mount  in  water  for  study. 

a.  Observe  with  a  low  power  the  spore-bearing  surface 
of  the  lamella.  l)o  you  find  brown  spores  in  groups 
of  four  scattered  over  the  surface  of  the  lamella  ? 
Do  you  find  basidia  and  paraphyses  as  described  in 
the  text  and  illustrated  in  Fig.  148,  c  ? 

I.  Draw  a  portion  of  your  section  to  bring  out  the  above 
points. 

c.  Examine  the  edges  of  your  specimen  for  basidia  bearing 
sterigniata  and  spores.  If  not  seen,  tease  the  speci- 
men in  pieces  with  dissecting  needles  and  observe 
the  edges  of  the  pieces.  Do  you  find  basidia  with 
four  sterigmata  and  young  spores,  and  basidia  with 
sterigniata  and  brown  spores  ?  How  are  these  spores 
formed  at  the  ends  of  the  sterigmata  ?  How  are  they 
shed  ?  Draw  a  basidium  with  sterigmata  and  spores. 

7.  Sections.    If  basidia  and  spores  are  not  found  satisfactorily 

in  the  above  material,  sections  of  the  lamellae  may 
be  used. 

PUFFBALLS 

(1KNERAL  APPEARANCE,  STRUCTURE,  AND  REPRODUCTION 

1.  Examine  puffballs  in  two  or  three  stages  of  development 

(Fig.  150)  to  determine  the  character  and  limits  of  the 
gleba  and  peridia.  Note  the  changes  in  these  two  layers 
as  the  puffballs  mature. 

2.  Examine  the  contents  of  mature  puffballs.    Some  puffballs 

have  indurated  fibers,  or  hypha-  (the  capillitium),  formed 
in  the  gleba  in  connection  with  the  spores. 

3.  Construct  a  drawing  to  show  the  relation  of  gleba  and 

peridia.    Draw  spores  and  capillitium. 


100          LABORATORY  AND  FIELD  EXERCISES 

RUSTS 

1.  Examine  leaves  of  cereals  or  other  plants  on  which  the 

different  kinds  of  spores  of  a  rust  are  borne.  Can  you 
see  differences  in  color  or  form  of  the  different  kinds 
of  rust  spores  ?  Are  the  spores  borne  in  groups  or 
masses  ?  -Where  is  the  mycelium  from  which  these 
spores  originated  ?  How  do  the  spores  become  exposed 
to  the  air  ?  On  how  many  and  what  kinds  of  hosts  are 
the  different  kinds  of  spores  borne  ? 

2.  Draw  the  stem  or  leaf  surfaces  on  which  spores  are  borne 

showing  the  groups  of  spores,  or  sori,  of  each  kind  pro- 
duced by  the  species  being  studied.  Name  the  host  and 
the  kind  of  spore  in  each  drawing. 

3.  Examine  the  different  kinds  of  spores  of  the  rust  micro- 

scopically. How  do  they  differ  ?  How  are  they  adapted 
for  distribution  and  wintering  ? 

4.  Draw  each  type  of  spore  in  some  detail. 

5.  Life  history.    How  many  hosts  are  infested  by  the  rust 

you  are  examining  ?  What  are  the  spring,  summer,  and 
winter  spores  ?  What  is  the  function  of  each  in  the  life 
history  ? 

SMUTS 

1.  Examine  corn  or  other  cereals  infested  with  smut.  Tease 
out  some  of  the  dark  mass  on  a  slide  and  examine  micro- 
scopically. What  is  the  composition  of  these  dark  smut 
masses  ?  Draw  some  smut  spores.  Where  is  the  plant 
which  gave  rise  to  the  spores  ?  Is  it  a  parasite  ?  How 
do  the  spores  become  exposed  to  the  air  ?  When  and 
how  do  these  spores  infect  a  new  crop  ? 


THE  PLANT  GKOUPS  101 

LICHENS 

Select  lichens  growing  on  bark  or  stones  and  observe  the 
following  points : 

1.  Color  of  upper  and  under  surface.    Moisten  lichens  and 

note  any  change  in  color.  What  gives  the  peculiar  color 
to  lichens  ?  Does  the  composition  of  the  compound 
plant  explain  its  peculiar  color  ? 

2.  The  form  of  lichens.    Observe  with  hand  lenses  the  lichens 

on  bark,  rocks,  etc.  Do  you  find  different  kinds,  or 
species,  of  lichens  recognizable  by  differences  in  size, 
color,  and  form?  See  the  kinds  of  lichens  on  the 
display  table. 

3.  Draw  one  or  two  lichens  to  illustrate  their  form. 

4.  Note  the  fruit  cups,  or  apothecia,  on  the  surface  of  some 

of  the  lichens.  These  cups  (Figs.  156  and  157  of  the 
text)  are  formed  of  spore  sacs  (asci)  which  bear  spores 
of  the  fungus  partner  of  the  lichen.  Draw  apothecia 
to  show  their  form  and  distribution. 

5.  Structure  of  the  lichen.    Moisten  a  small  piece  of  a  lichen 

thallus  and  tear  in  pieces  in'  a  drop  of  water  on  a  slide. 
Cover  and  crush  out  under  a  cover  glass.  Observe  the 
fungus  hyphse  and  the  algse  which  compose  the  plant 
body. 

a.  The  algae.    Note  their  form,  color,  and  relation  to  the 

fungus  hyphte.  The  latter  grasp  the  algae  with  mi- 
nute branches  and  absorb  food  from  them.  Are  the 
alga?  multiplying  by  division  ? 

b.  TJie  fungus  portion  of  the  lichen.    Observe  the  hyphae  of 

the  fungus.  What  is  their  structure?  Draw  the 
algae  and  fungus  mycelium  comprising  the  lichen. 

6.  Summary.    Summarize  the  work  of  the  two  partners,  the 

fungus  and  the  alga,  in  the  life  of  the  lichen. 


102         LABORATORY  AM)   FIKLI)  KXKllCISKS 

LILAC  MILDEW  (MICROSPHAERA  ALX/) 

1.  Structure.    Observe  the  upper  surface  of  leaves  infected 

with  the  parasite  and  note 

a.  The  white  mycelium  covering  the  leaf  surface  with  a 
whitish  mass  of  hyphse.  Is  this  the  plant  body  of 
the  fungus  ?  How  is  it  anchored  to  the  leaf  and  how 
nourished  ?  "What  is  the  structure  of  the  body  of 
the  plant? 

2.  Reproduction  by  ascocarps,   or   fruits.    These  are   dark 

bodies  scattered  over  the  surface  of  the  leaf. 

a.  Distribution  of  the  ascocarps.    Outline  a  portion  of  a 

leaf  surface,  showing  the  distribution  of  the  mycelium 
and  the  ascocarp  fruits  on  a  leaf. 

b.  Structure  of  ascocarps  and  asci.    Remove  ascocarps  to  a 

slide  in  a  drop  of  alcohol  and  glycerin  by  scraping 
them  from  a  leaf  with  a  needle.  Avoid  scraping  off 
dirt  and  portions  of  the  leaf.  Note  with  low  power 

(1)  The  dark  wall  and  app<'n<l<i</<'x.  The  structure  of  the 

wall  can  be  ascertained  by  slight  crushing.  Note 
its  cellular  structure  if  it  is  not  too  dark.  Note 
the  shape  and  attachment  of  the  appendages  to 
the  wall  of  the  fruit.  Draw  a  fruit  body  and  one 
or  two  appendages. 

(2)  Asci  and  ascospores.  These  are  obtained  by  crush- 

ing ascocarps  under  a  cover  glass  with  a  needle. 
How  do  asci  and  spores  get  out  of  the  fruits  in 
nature  ?  When  will  spores  be  liberated  and  dis- 
seminated ?  How  disseminated  ? 

(3)  Spores.    Note  their  shape  and  the  number  in  each 

ascus.  . 

3.  Drawings.    Draw  a  fruit  body  from  which  asci  are  being 

pressed  out.    Draw  an  ascus  and  spores. 


SECTION  VII.    BRYOPIIYTA  (LIVERWORTS 
AND  M«  ISSES 

A.  HEPATICAE  (LIVERWORTS) 
GAMETOPHYTE 

The  following  outline  for  laboratory  work  is  based  upon  the 
relation  of  structure  to  function  in  liverworts.    The  outlines 
are  made  so  general  in  their  nature  that  any  one  of  several 
species  of  thallose  liverworts  may  be  used.    The  term  thaUus 
applies  to  a  plant  body  without  true  roots,  stem,  and  leaves. 
1.  Habitat.    From  observations  of  living  material  and  text 
figures  and  descriptions  determine  whether  liverworts 
are  typically   mesophytic,  hydrophytic,  or  xerophytic 
in  habitat. 
i'.  Habit  and  growth. 

a.  The  apical   meristem   of   liverworts   is   located  in  the 

Hutches,  or  indentations,  at  the  ends  of  the  green 
lobes  of  the  plant  body,  or  thallus.  With  this  knowl- 
edge determine  the  method  of  elongation  and  repeated 
forking  (dichotomy)  of  the  branches.  How  is  the 
I'-Kte  form  or  •/>}(*  and  similar  liverworts 

attained  by  this  method  of  growth  ?  How  would 
new  independent  individuals  arise  from  a  rosette, 
or  colony  of  branches  ?  Is  this  a  form  of  asexual  or 
of  vegetative  reproduction  ? 

b.  Sketch  a  liverwort  with  several  lobes,  or  branches. 

c.  Discuss   briefly  in  your  notes  the   method  of  growth 

and  the  formation  of  rosettes  and  of  new  individuals. 
103 


104          LABORATORY  AXD  FIELD  EXERCISES 

3.  Structure  and  function. 

a.  Adaptations  for  absorption. 

(1)  Observe  with  a  hand  lens  the  ventral  surface  of 

liverworts  which  have  been  freed  from  soil. 
What  structures  do  you  find  ?  Mount  and  study 
under  a  compound  microscope.  How  do  these 
structures  (rhizoids)  differ  from  true  roots  ?  What 
other  structures  do  you  find  and  how  are  they 
related  to  the  plant  body  ?  Do  these  structures 
have  any  particular  function  ? 

(2)  Sketch  the  lower  surface  of  the  liverwort,  indicat- 

ing the  position  of  the  structures  seen.  Label 
rhizoids  and  scalelike  leaves.  Draw  more  in 
detail  one  or  more  rhizoids. 

b.  Light  relation  and  photosynthesis. 

(1)  Is  the  general  form  of  the  liverwort  thallus  adapted 

for  photosynthesis  ?  Be  able  to  explain.  Examine 
the  dorsal  (upper)  surface  of  the  thallus  with  a 
hand  lens.  Do  you  find  anything  corresponding 
to  stomata  and  the  green  mesophyll  areas  of  leaves 
of  the  higher  plants?  Thin  surface  sections 
should  be  examined  if  difficulty  is  experienced 
in  determining  the  structure  of  the  dorsal  surface. 

(2)  Sketch  accurately  the  structure  of  the  dorsal  surface 

of  the  thallus  as  it  appears  under  the  hand  lens 
or  low  power. 

(3)  Sections.    Study  sections  cut  vertically  through  the 

plant  body,  using  low  powers  of  the  compound 
microscope  or  a  good  dissecting  microscope.  Com- 
pare the  structure  of  the  dorsal  portion  of  the 
liverwort  with  that  of  a  green  leaf.  Are  there 
air  spaces  and  an  internal  atmosphere  ?  What 
is  the  disposition  of  green  chlorophyll  cells  ? 


THE  PLANT  GROUPS 


105 


Do  you  find  stomata?  What  kind  of  tissue  is 
below  the  green  chlorenchyma  ?  What  is  its 
function  ?  Outline  the  section  and  detail  a  small 
portion  of  its  cellular  structure.  Label  correctly. 
Summarize  the  adaptations  of  the  thallus  of  the 
liverwort  for  photosynthesis  and  absorption. 


FIG.  22.    A  common  liverwort  (Marchantia) 

A,  antheridial  plant;  I],  archegonial  plant,  rh,  rhizoids,  and  m,  midrib,  of  the 
leaf  like  flattened  body  /;  c,  capsules  in  which  vegetative  reproductive  buds  are 
formed  ;  s,  upright  stalks  (a,  antheridial  and  ar,  archegonial,  the  latter  being  dis- 
tinguished by  peculiar  rays  r).  Slightly  more  than  natural  size.  From  Bergen 
and  Caldwell's  "  Practical  Botany  " 

c.  Storage  and  conduction.    Are  there  any  such  structural 
devices  for  storage  of  reserve  foods  and  for  conduc- 
tion of  water  and  foods  in  liverworts  as  we  have 
found  in  the  higher  plants  ?    Be  able  to  explain. 
4.  Reproduction.    If  Marchantia  is  used  for  the  following 
study,  the  peculiar  reproductive  branches  (receptacles) 
will  need  to  be  explained  by  the  teacher. 
a.  Distribution  of  sex  organs. 

(1)  Study  the  distribution  of  sex  organs  on  the  dorsal 
surface  of  the  thallus  in  llicciocarpus,  ConocepJmlus, 


106 


LABORATORY  AND  FIELD  EXERCISES 


or  similar  liverworts,  using  a  hand  lens.  Are 
the  male  and  female  organs  aggregated  or  scat- 
tered over  the  surface  ?  Are  the  plants  monoecious 


FIG.  23.    The  female  receptacle  of  Marchantia 

A,  portion  of  a  lengthwise  section  of  a  young  receptacle 
(semidiagrammatic),  showing  a  row  of  archegonia  hanging 
down  from  the  lower  surface,  the  youngest  heing  nearest 
the  stalk  (air  chambers  are  present  on  the  upper  surface) ; 
I,  one  of  the  ringerlike  lobes  back  of  the  section  (the  diamond- 
shaped  areas  indicate  air  chambers).  B,  a  young  sporo- 
phyte  within  the  parent  archegonium  (the  region  which  is  to 
become  the  spore  case  is  indicated  by  the  cross  lines,  and 
the  small  foot  is  attached  to  the  base  of  the  archegonium) ; 
e,  a  special  envelope  developed  around  the  archegonia  of  Mar- 
chantia. From  Bergen  and  Davis's  "  Principles  of  Botany  " 


(with  male  and  female  organs  in  separate  groups 
on  the  same  thallus)  or  dicecious  (with  male  and 
female  organs  on  separate  plants  ?  If  the  organs 
are  separate,  how  is  fertilization  to  take  place  ? 
(2)  Sketch  plants,  showing  the  distribution  of  sex 
organs.  Label. 


THE  PLANT  GROUPS  107 

b.  Archegonia  and  antlieridia  (structure  of  sex  organs). 
Study  sections  of  plants  cut  so  as  to  show  the  form 
and  structure  of  the  sex  organs. 

(1)  Note  in  each  organ  an  outer  layer  and  a  central 

column  of  cells.  What  is  the  cellular  structure 
of  these  two  groups  of  cells  ?  the  function  of 
each  ?  Are  these  cell  groups  alike  in  the  female 
organ,  or  archegonium,  and  in  the  male  organ, 
or  antheridium  ?  If  sex  organs  of  different  ages 
are  availahle,  note  the  method  of  liberating  sperms 
and  exposing  the  eggs  for  fertilization. 

(2)  Comparisons.  How  do  the  archegonia  and  the  antlie- 

ridia of  the  liverwort  differ  from  the  gametangia 
(oogonia  and  antheridia)  of  alga?  and  fungi  ?  Are 
archegonia  and  antheridia  better  adapted  for  secur- 
ing the  development  of  gametes  and  fertilization 
in  amphibious  plants  like  liverworts  than  the 
gametangia  of  algffi  and  fungi  ?  Be  able  to  explain. 

(3)  Write  a  brief  summary  of  the  structure  and  adapta- 

tions of  the  sex  organs  in  liverworts.  Indicate 
also  the  important  distinctions  between  arche- 
gonia and  antheridia  and  the  gametangia  of  algse 
and  fungi. 

(4)  Draw  diagrams  illustrating  the  structure  of  each. 

Study  the  structure  of  the  sex  organs  in  the  text 
and  label  parts  of  your  figures  accurately. 

SPOROPIIYTE  AXD  LIFE  HISTORY 

1.  Sporophyte.  Study  sporophytes  of  Ricciocarpus  or  other 

liverworts  by  dissection  and  in  sections. 
a.  Structure.    What  kinds  of  tissues  and  cells  are  found 
in  the  sporophyte  that  you  are  examining  ?    What 
is  the  apparent    function   of  the  tissues  and   cells 


108          LABORATORY  AND  FIELD  EXERCISES 

observed  ?  Draw  the  sporophyte  or  the  sporophyte  and 
surrounding  tissues  if  studied  in  section.  Label  the 
parts  according  to  function. 

b.  Dissemination  of  spores.   Are  there  any  distinct  devices 

for  spore  dissemination  in  the  sporophyte  that  you 
are  studying  ?  How  would  the  spores  be  liberated  ? 
What  is  the  nature  of  the  spore  cell  and  how  is  it 
adapted  for  dissemination  and  for  withstanding  dessi- 
cation,  or  drying,  by  wind  and  sun  ? 

c.  Comparisons.    Is   the  sporophyte   a  new   structure   in 

plants  studied  thus  far  ?    What  is  its  particular  use, 
or  function,  in  the  life  history  of  the  amphibious 
liverworts  ?    Would  such  a  structure  be  equally  use- 
ful in  the  life  history  of  the  fresh-water  algse  ? 
2.  Life  history.    Write  a  graphical  life  history  of  the  liver- 
wort that  you  are  studying,  similar  to  the  life  histories 
already  written  for  Spirogyra  and  fungi.    Explain  in 
your  notes  the  special  adaptations  of  the  gametophyte 
and  the  sporophyte  to  seasonal  conditions  and  changes. 

B.  MUSCI  (MOSSES) 
GAMETOPHYTE 

1.  Habitat.  What  is  the  usual  habitat  of  mosses  ?  Are  they 
for  the  most  part  mesophytes,  hydrophytes,  or  xero- 
phytes  in  habitat  and  structure  ?  Do  you  know  of 
exceptions  to  the  general  rule  ?  Can  you  think  of  ad- 
vantages to  be  derived  from  the  clustered  habit  of 
growth  of  the  mosses  ?  Would  this  habit  be  of  any 
advantage  in  securing  food,  moisture,  and  light,  or  in 
insuring  fertilization  of  eggs  by  the  motile  sperms  of 
mosses  ?  Summarize  your  ideas  of  habitat  in  your 
notes. 


THE  PLANT  GROUPS  109 

2.  Habit.    Wash  the  earth  from  some  moss  plants  and  pre- 

pare them  for  study.    Observe  the  parts  of  the  plant 

body  and  compare  them  with  those  of  higher  seed  plants. 

a.  Plan  of  the  plant  body.    Is  the  central  axis  divided 

into  regular  nodes  and  intemodes  ?    Are  there  lateral 

and  terminal  buds  ?    Are  the  leaves  cyclic  or  spiral 

in  arrangement  ?  Have  the  hairlike  roots,  or  rhizoids, 

any  definite  points  of  origin  on  the  stem  ?    Do  roots 

and  leaves  have  any  definite  tropic  response  ?  Sketch 

a  stem,  using  outline  figures,  to  indicate  the  relation 

of  parts  of  the  plant  body  of  the  moss. 

b.  Study    the    microscopic   structure   of    the   leaves    and 

rhizoids  and  indicate  the  cellular  structure  of  these 

organs  by  accurate  drawings. 

3.  Reproduction.    Study  plants  which  have  antheridia  and 

archegonia  in  the  terminal  buds.    The  males  may  be 
recognized  as  open  disks,  or  clusters  of  antheridia,  ter- 
minating the   stem.    The  female  plants   have  similar 
clusters  of  archegonia  borne  in  closed  buds. 
a.  Male  disks  and  antheridia.    Cut  off  the  male  head  and 
dissect  it  out  in  a  drop  of  water  on  a  slide. 

(1)  What  is  the  shape  of  the  moss  antheridium  ?    its 

structure  ?  Is  it  composed  of  different  cell  layers  ? 
How  do  these  layers  differ  in  structure  ?  What 
function  do  you  consider  that  each  cell  group, 
or  layer,  has  in  the  development  and  liberation 
of  sperms  ?  Do  you  find  other  cell  structures 
among  the  antheridia  ?  Sterile  cell  chains,  called 
paraphyses,  exist  among  the  antheridia  of  most 
mosses,  which  probably  protect  the  developing 
antheridia. 

(2)  Draw  antheridia  and  paraphyses.   Label  the  parts  of 

the  antheridium  according  to  position  and  function. 


110          LABORATORY  AND  FIELD  EXERCISES 

(3)  If  sections  of  antheridia  are  available,  study  in  some 
detail  the  structure  of  the  outer  protective  layers 
of  the  antheridium  and  the  inner  sperm  mother 
cells.  Make  an  accurate  drawing  of  a  section  of 
an  antheridium. 

b.  Female  heads.  Observe  the  difference  in  appearance  of 
male  and  female  heads  in  mosses.  Dissect  out 
female  heads,  as  for  the  males  above,  or  study 
sections  cut  through  female  heads  of  a  moss. 

(1)  Sections.    If  .sections  are  studied,  note  the  origin  of 

the  archegonia  from  the  apical  meristem  of  the 
rnoss  stem.  What  is  the  form  and  structure  of 
the  archegonium  ?  Is  there  an  outer  protective 
layer  and  a  central  column  of  cells  as  in  the 
antheridium  ?  Find  the  egg  in  the  basal  swollen 
part  (venter)  of  the  archegonium.  Detail  one  or 
more  archegonia  and  cells  of  the  meristem  from 
which  they  arise. 

(2)  Dissections.    If  slides  are  not  available,  archegonia 

may  be  dissected  out  of  female  heads  as  for 
antheridia  above.  Draw  archegonia  if  found  by 
this  method,  indicating  the  structure  of  the  outer 
protective  layer  and  of  the  central  column  of 
cells.  See  the  account  of  the  structure  of  the 
archegonium  under  Ricciocarpus  and  the  moss 
in  the  text. 

(3)  Comparisons.   Compare  the  archegonium  of  the  moss 

and  the  oogonium  (gametangium)  of  algte.  How 
do  they  differ  ?  In  what  respects  is  the  arche- 
gonium better  adapted  for  insuring  fertilization 
in  land  plants  than  the  simple  gainetangia  of 
the  algae  ? 


THE  PLA^T  GROUPS  111 

SPOROPHYTE 

1.  Mature  sporophyte.  Select  a  moss  plant  bearing  a  mature 
sporophyte  and  study  the  relation  of  the  gametophyte 
and  sporophyte. 

a.  Cut  away  the  gametophyte  on  one  side  so  as  to  expose 
the  base  of  the  sporophyte.    Is  the  sporophyte  a  para- 
site on  the  gametophyte  ? 
b.  Parts  of  the  sporophyte. 

(1)  Study  sporophytes   carefully  with  the   naked    eye 

and  with  a  hand  lens.  Is  the  enlarged  part  (cap- 
sule) differentiated  into  parts  ?  Note  its  connection 
with  the  gametophyte.  Draw  the  sporophyte  and 
label  its  parts  after  reading  the  text  description 
of  the  sporophyte. 

(2)  Operadum,  peristome,  and  spores.    With  dissecting 

needles  remove  the  operculum  and  expose  the 
peristome.  What  is  its  structure  in  the  moss 
that  you  are  studying  ?  How  many  teeth  are 
there  in  the  peristome  ?  Breathe  on  the  peristome 
teeth  and  observe  quickly  under  low  power. 
What  is  the  nature  of  the  movement  of  the 
teeth  ?  What  is  the  function  of  this  movement 
in  the  scattering  of  spores  ?  Draw  a  portion  of 
the  peristome  as  seen  under  low  and  high  powers. 

(3)  Spores.   Remove  spores  from  a  capsule  with  needles 

and  note  their  size,  form,  and  structure.  Is  a 
spore  a  cell  ?  Is  it  a  reproductive  cell  ?  How  is 
it  adapted  to  dissemination  and  to  resistance  to 
the  effects  of  sun  and  drought  ?  How  do  these 
spores  differ  from  spores  of  the  algae  ? 

(4)  Spore  germination.    What,  do  moss  spores  produce 

when  they  germinate  ?    See  text  and  laboratory 


112          LABORATORY   AND  FIELD  EXERCISES 

material  if  available.    How  does  the  leaf}-  moss 

gametophyte  arise  ? 

2.  Embryo  and  young  sporophyte.  Study  stages  in  the 
development  of  the  sporophyte.  What  relation  does 
the  old  archegonium  wall  sustain  to  the  growing  sporo- 
phyte ?  to  the  mature  capsule  ?  Draw  stages  in  the 
development  of  the  sporophyte.  Label  sporophyte  and 
old  archegonium  after  reading  the  text  discussion  of 
these  structures. 

LIFE  HISTORY  AND  SEASONAL  HISTORY 

1. .  What  are  the  two  alternating  generations  of  the  moss, 
and  how  do  they  differ  from  similar  stages  in  Ricdo- 
carpus  ?  See  the  life  history  of  Ricciocarpus  in  the  text. 

2.  Write  a  graphical  life  history  of  the  moss  plant,  using 

outline  figures.  Indicate  in  the  history  the  protonema 
and  gametophyte,  and  stages  in  the  development  of 
the  sporophyte. 

3.  Seasonal  history  and  alternation  of  generations. 

a.  Are  the  mosses  annuals,  biennials,  or  perennials  in 

habit  ?  How  do  they  pass  the  winter  ?  Determine 
the  main  nutritive  and  reproductive  seasonal  activities 
of  common  mosses.  Contrast  the  seasonal  history 
of  mosses  with  that  of  higher  plants  outlined  in  an 
earlier  part  of  the  text.  Are  the  alternating  genera- 
tions related  to  seasonal  life  ?  If  so,  how  ?  Would 
tli is  seasonal  relation  be  different  in  different  mosses  ? 
Investigate  this  point  for  yourself  as  far  as  possible 
by  studies  of  mosses  out  of  doors  and  in  textbooks. 

b.  Write  a  brief  account  of  your  findings  on  the  above 

points  and  hand  in  with  your  drawings. 


SECTION  VIII.   PTERIDOPHYTA  (FERNS, 
EQUISETA,  AND  LYCOPODS) 

The  Pteridophyta,  as  indicated  in  the  text,  are  the  plants 
from  which  the  higher  plants  had  their  origin  in  geologic 
periods  earlier  than  the  present  era.  Their  organization  and 
life  history  are  therefore  of  especial  interest  in  interpreting  the 
structure,  ecology,  and  life  history  of  the  higher  plants.  In 
order  to  make  clear  the  contrasts  and  similarities  between  the 
Filicales,  or  true  ferns,  and  the  higher  seed  plants,  the  following 
laboratory  directions  are  written,  from  the  same  standpoint  and 
with  similar  headings  and  references  as  the  directions  on  the 
higher  herbaceous  and  woody  plants  of  Part  I.  Constant  refer- 
ence is  also  made  to  the  earlier  work  of  the  student,  and  to 
the  text  dealing  with  the  organization  and  adaptations  of  higher 
plants  to  the  environment. 

A.  FILICALES 
SPOROPHYTE 

Select  for  study  one  or  more  species  of  common  wild  and 
cultivated  ferns  which  show  both  mature  and  young,  growing 
leaves.  Wash  the  earth  carefully  from  stem  and  roots  of  at 
least  one  specimen  and  study  as  follows : 

1.  Plan  of  the   plant  body.    Compare  the  general  plan  of 

the  plant  body  of  a  fern  with  that  of  herbaceous  and 

woody  plants  studied  earlier  in  the  course,  and  with 

such  seed  plants  as  may  be  available  for  comparison. 

a.  Is   the   central   axis,  or  stem,  divided   into   nodes  and 

internodes,  with  regular  points  of  origin  for  leaves 

113 


114          LABOKAT011Y  AND  FIELD  EXERCISES 

and  roots  ?  Are  there  lateral  and  terminal  buds  ? 
How  does  the  terminal  bud  of  ferns  differ  from  that 
of  higher  plants  ?  Can  you  think  of  reasons  for  the 
differences  observed  ?  Are  there  lateral  branches, 
and  if  so,  have  they  a  definite  arrangement  ?  Observe 
the  ramenta,  or  brown  scales,  characteristic  of  ferns 
on  the  stem,  leaf  bases,  and  young  leaves.  What  is 
the  probable  function  of  these  ramenta  as  the  ter* 
minal  bud  unfolds  in  the  spring  ? 

2.  Leaves. 

a.  Mature  leaves.    Contrast  the  mature  leaves  of  ferns  with 

those  of  higher  plants  in  size,  form,  texture,  and 
venation.  What  are  the  distinctive  characteristics 
of  fern  leaves  accessible  to  you,  and  of  fern  leaves 
known  to  you,  as  compared  with  those  of  higher 
seed  plants  ?  Study  the  mode  of  venation  and  the 
termination  of  the  veins,  comparing  ferns  and  some 
common  seed  plants  in  this  respect. 

b.  Young  leaves.    Study  the  growth   and  form   of  young 

leaves  of  the  terminal  bud.  What  are  the  distinctive 
characters  of  young  fern  leaves  as  regards  form  and 
method  of  growth  ? 

3.  Roots.    Study  the  mode  of  brandling  of  roots.    Is  there 

any  distinctive  feature  which  characterizes  ferns  in 
this  respect  as  compared  with  higher  plants  ?  Deter- 
mine also  the  origin  and  distribution  of  roots  on 
the  stem. 

4.  Adjustments   to   the   environment   by  tropisms  (see  the 

text,  Part  I,  and  earlier  laboratory  work  on  tropisms). 
Determine  the  tropisms  of  the  stem,  roots,  and  leaves 
of  ferns  and  apply  proper  terms  to  indicate  the  nature 
of  stimulus  and  response,  —  for  example,  protropic, 
apotropic,  and  diatropic. 


THE  PLANT  GROUPS  115 

5.  Distinctive  characteristics.  Summarize  in  your  notes 
under  the  above  headings  (namely,  body  plan,  leaves, 
roots,  and  the  tropisms  of  the  central  axis  and  lateral 
organs)  the  distinctive  characteristics  of  ferns  as  com- 
pared with  higher  plants. 
0.  Drawings. 

a.  Make  an.  accurate  drawing  of  the  fern  examined. 
I.  Bring  out  as  largely  as  possible,  in  the  main  drawing 
and,  where  necessary,  by  detailed  drawings  of  certain 
organs  (for  example,  leaves),  the  distinctive  charac- 
teristics of  ferns  named  above  under  5. 
c.  Draw  an  outline  figure,  indicating  the  positions  assumed 
by_the  organs  in  a  cultivated  or  wild  fern.    Indicate 
stimuli  and  the  nature  of  the  response  of  the  plant 
organs  by  use  of  the  proper  terms,  as  in  the  earlier 
studies  of  seed  plants  in  Part  I. 
7.  Habitat,  habit,  and  environment. 

a.  Habitat.    What  is  the  common  habitat  of  ferns  in  your 

region  ?  Are  they  typically  mesophytic,  xerophytic, 
or  liydrophytic  ?  Do  you  know  of  exceptions  to  the 
general  rule  ? 

b.  Environment.    Compare  the   environment   of  common 

wild  ferns  growing  on  the  forest  floor  with  ferns 
growing  in  homes,  and  with  common  seed  plants 
growing  in  the  open.  How  would  these  three  habi- 
tats compare  as  regards  heat,  light,  soil  water,  food 
elements  in  the  soil,  and  the  relative  humidity  of 
the  air  ?  Answer  these  questions  in  a  paragraph 
in  your  notes. 

c.  Habit.  How  is  the  habit  of  wild  ferns  especially  adapted 

to  the  above  environment  as  regards  the  form,  size, 
and  texture  of  the  leaves  ?  Do  cultivated  ferns  mani- 
fest a  different  structure  ? 


116         LABORATORY  AND  FIELD  EXERCISES 

d.  Seasonal  life.    Are  ferns  annuals,  biennials,  or  peren- 

nials in  habit  ?  How  do  they  pass  the  winter  ?  What 
is  the  function  of  the  rhizome  in  the  winter  season  ? 
Be  able  to  indicate  the  seasonal  activities  of  the  fern 
in  a  manner  similar  to  that  outlined  for  the  bean, 
clover,  and  apple  in  Part  I  of  the  text. 

e.  Summarize  the  principal  seasonal  activities  of  the  fern 

plant  during  summer,  spring,  and  winter,  indicating 

the  main  plant  organs  concerned. 

8.  Anatomy  of  maidenhair  fern  (Adiantum).  Examine  with 
a  hand  lens  and  low  powers  of  the  microscope  trans- 
verse sections  of  a  fern  stem,  or  rhizome,  like  that  of 
Adiantum,  with  a  tubular  vascular  cylinder  of  phloem 
and  xylem. 

a.  Gross  arrangement  of  tissues.    Do  you  find  the  same 

general  tissue  layers  in  the  fern  rhizome  as  in  the 
herbaceous  stems  studied  earlier  in  the  course  ? 
(Consult  figures  and  text  discussion  on  herbaceous 
stems.)  Are  there  the  same  general  subdivisions  of 
the  cortex  into  stereome  and  storage  tissues,  and  of 
the  vascular  ring  into  phloem,  cambium,  and  xylem 
as  in  herbaceous  stems  ?  Note  the  relative  width  of 
the  cortex,  vascular  cylinder,  and  pith  in  the  fern 
and  in  herbaceous  and  woody  stems. 

b.  Leaf  traces  and  leaf  gaps.  Study   sections  of  a  fern 

rhizome  cut  through  the  point  of  exit  of  a  leaf. 
(1)  Is  the  vascular  cylinder  broken,  forming  a  break, 
or  gap,  with  a  small  leaf  bundle  (the  leaf  trace) 
in  section  opposite  the  gap  ?  Consult  the  text 
descriptions  and  fix  clearly  in  mind  the  nature 
and  relations  of  leaf  trace,  leaf  gap,  and  the  vas- 
cular cylinder  as  a  whole.  See  also  the  text 
figures  on  the  anatomy  of  Adiantum. 


THE  PLANT  GROUPS  117 

(2)  Root  traces.  The   root   bundles    which  enter  the 

lateral  roots  may  sometimes  be  found  leaving 
the  vascular  cylinder.  Do  they  leave  a  gap  as  in 
the  leaf  bundle  ? 

(3)  Drawing.    Outline  your  entire  section,  indicating 

the  main  tissue  layers  and  their  subdivisions  and 
the  relations  of  leaf  trace,  leaf  gap,  and  cen- 
tral cylinder.  How  does  Adiantum  differ  from 
an  herbaceous  plant  like  Salvia  in  its  gross 
anatomy  ?  Consult  the  text  discussion  of  Salvia 
in  Part  I. 
e.  Minute  structure  of  the  tissues. 

(1)  Epidermis,  cortex,  and  pith.    Draw  in  detail  a  few 

characteristic  cells  of  each  of  the  above  layers 
and  their  main  subdivisions,  to  show  the  dis- 
tinctive cell  characteristics  of  each  tissue.  Label 
the  parts  of  the  cells.  What  is  the  function  of 
eacli  cell  type  in  the  rhizome,  and  how  is  its 
structure  adapted  to  its  function  ? 

(2)  Vascular  cylinder.    Study  the  following  tissues  of 

the  vascular  ring  and  leaf  trace  critically  with 
low  power : 

(«)  Xylem.  Characterized  by  large  water-carrying 
cells  resembling  ducts  in  higher  plants. 
These  xylem  cells,  or  tracheids,  stain  red 
where  sections  are  stained  with  safranin 
(the  dye  commonly  used  in  staining  xylem). 
Are  there  rays  or  other  living  tissues  in  the 
xylem  of  ferns,  as  in  that  of  higher  seed 
plants  previously  studied  ? 

(7>)  Pldoe'm.  Surrounding  the  xylem.  The  sieve 
tubes  are  the  large  cells  seen  in  the  phloem 
flanking  the  xylem  on  either  side. 


118          LABORATORY  AND  FIELD  EXERCISES 

(c-)  Cambium.  Is  there  any  evidence  of  a  cambium 
composed  of  regular  cells  as  in  higher  plants  ? 

(d)  Endodermis.  A  dark-brown  layer  surrounding 
the  phloem,  beneath  which  is  a  single  cell 
layer  containing  starch,  called  the  pericycle. 

(Y)  Does  the  leaf  trace  have  the  same  structure  as 
the  main  vascular  cylinder  ? 

(3)  Drawing.    Make  a  cellular  drawing  of  a  small  por- 

tion of  the  main  vascular  cylinder,  or  of  the  leaf 
trace  to  show  the  structure  of  the  tissue  elements. 
Label  correctly. 

(4)  Summary.    Summarize  the  distinctive  features  of 

the  tissue  arrangements  in  the  fern  as  compared 
with  that   of   herbaceous  dicotyledons.    See  the 
summary  of  the  anatomy  of  herbaceous  stems  in 
Part  I  of  the  text. 
9.  Anatomy  of  eagle  fern  (Pteris  aquilind). 

a.  Gross  anatomy.  Study  transverse  sections  of  the  eagle 

fern,  as  indicated  above  for  Adiantum,  using  a  hand 

lens  first  and  then  low  powers  of  the  microscope. 

Compare  the  main  tissue  layers  with  those  of  the 

maidenhair  fern. 

(1)  Epidermis  and  cortex.  Are  both  epidermis  and  cor- 

tex present,  and  do  they  have  the  same  cell  char- 
acteristics as  in  the  maidenhair  fern  ?  Is  there 
an  exoskeleton  in  Pteris? 

(2)  Vascular  ring.   Study  the  vascular  system  carefully 

with  a  hand  lens  and  low  power.  Is  there  any- 
thing corresponding  to  the  single  vascular  ring  of 
Adiantum  ?  What  kinds  of  tissue  masses  occupy 
the  pith  region  ?  Do  you  find  central  skeletal,  or 
strengthening,  masses  and  vascular  strands  ?  See 
text  discussion  of  the  eagle  fern  (Pteris  aquilina). 


THE  PLANT  GROUPS  119 

(3)  Drawings.  Construct  an  outline  figure  (no  cells) 
of  the  cross  section  of  the  stem  of  Pteris.  Label 
the  parts  accurately.  Discuss  briefly  the  distinc- 
tive features  of  the  anatomy  of  the  eagle  fern  as 
compared  with  that  of  Adiantum. 
o.  Minute  anatomy. 

(1)  Transverse  sections.  Work  out  and  draw  the  cellu- 

lar structure  of  one  vascular  strand  of  the  rhizome 
in  Pteris  and  label  accurately.  Draw  also  a  few 
cells  of  the  epidermal,  of  the  skeletal,  and  of  the 
storage  tissues. 

(2)  Long  sections. 

(a)  /Skeletal  tissue.  Work  out  and  draw  a  few  cells 
of  the  strengthening,  or  skeletal,  tissue  as 
seen  in  long  section.  Are  these  cells  living  ? 
What  are  their  most  distinctive  structural 
characteristics?  Explain  in  your  notes. 

(5)  Vascular  tissues.  Study  the  vascular  tissues 
in  long  section.  Find  the  sieve  tubes  of  the 
phloem  and  water-conducting  cells,  or 
tracheids,  of  the  xylem.  Determine  the 
«  shape,  size,  and  wall  markings  of  each  type 

of  cell  element. 

(c)  Sieve  tubes.    Find  in  the  sections  the  abundant 

sieve  plates.  Consult  text  figures.  Be  able 
to  discuss  the  structure  and  function  of  the 
sieve  plates.  Draw  accurately  one  or  more 
sieve  tubes  and  the  adjoining  cells. 

(d)  Tracheids.    Study  the  form,  cell  contents,  and 

cell-wall  thickening  of  the  tracheids.  How 
does  the  tracheid  differ  from  the  duct,  or 
vessel,  of  the  higher  plants  ?  Is  it  as  efficient 
in  water  conduction  as  the  vessels  are? 


120          LABORATORY  AND  FIELD  EXERCISES 

Determine  with    care  the   thick  and  thin 
areas  of  the  wall.    Which  area  constitutes 
the  greater  portion  of  the  entire  wall  of  the 
tracheid?    What  is  the  function  of  each  in 
the  work  of  the  tracheid  and  the  stem? 
(e)  Summary.   Draw  and  discuss  briefly  the  struc- 
ture and  functions  of  the  tracheids  as  com- 
pared with  the  ducts  of  the  higher  plants. 
10.  Asexual  reproduction. 

a.   The  sorus.  Observe  the  lower  (abaxial)  surface  of  fern 
leaves  for  clusters  of  fern  sporangia,  or  sori. 

(1)  What  is  the  position  of  the  sori  with  reference  to 

the  veins  ?  Can  you  think  of  a  reason  for  this 
position  ?  Are  the  sori  numerous  or  infrequent 
on  the  leaves  that  you  are  examining?  What 
advantages  has  the  fern  sporophyte  over  the  moss 
sporophyte  in  the  production  of  spores  ?  See  text 
discussion  for  the  number  of  fern  spores  pro- 
duced by  a  single  sporophyte  annually. 

(2)  Structure   of  the  sorus.  With  hand  lens  and  low 

power  of  the  microscope  determine  the  structure 
of  the  sorus.  Has  it  a  covering  ?  Do  sori  of  dif- 
ferent ages  have  a  different  color  and  appearance  ? 
To  what  is  this  difference  in  color  due  ?  Where 
there  is  a  membranous  covering  (indusium),  note 
its  form  in  young  sori,  and  the  method  by  which 
the  brown  sporangia  became  exposed  to  the  air 
in  older  sori.  If  different  species  of  ferns  are 
available,  observe  sori  and  indusia  of  different 
shapes  and  forms.  Draw  a  single  pinnule  of  a  fern 
to  show  the  form,  structure,  and  distribution  of 
the  sori.  Compare  the  indusia  in  your  specimens 
with  those  shown  in  the  text  (Figs.  168  and  176). 


THE  PLA^T  GROUPS  121 

b.  Sporangia  and  spores. 

(1)  Dissect  out  sporangia  into  a  drop  of  water  on  a 

slide.  Mount  and  study  the  cellular  structure  of 
the  sporangium  carefully.  Are  the  cells  all  alike 
in  structure  and  in  function?  To  demonstrate 
this  point  remove  sporangia  to  a  dry  slide.  Breathe 
on  them  gently  and  observe  quickly  under  low 
power.  Result?  Consult  the  text  discussion  of 
spore  dissemination. 

(2)  Draw  accurate  diagrams  of  a  closed  and  an  open 

sporangium  as  you  observe  them  in  your  own 
preparations.  Be  prepared  to  explain  the  peculiar 
structure  and  mechanism  of  the  annulus. 

SUPPLEMENTARY  STUDIES 

1.  Sporogenesis.    If  slides  are  available,  the  essential  stages  in 
sporogenesis,  or  spore  forumtion,  may  be  worked  out,  illustrating 
the  archesporium  and  tapetum,  the  sporogenous  and  spore  mother- 
cell  stages,  and  the  formation  of  tetrads  and  spores. 

2.  Analysis   and   classification.    Each   student  should  learn  to 
use  the  analytical  key  and  analyze  a  few  species  of  common  ferns. 
Record  your  analyses  as  follows  : 

«.  Family  —  

b.  Genus  —  


c.  Species:  scientific  name, ;  common  name, 

GAMETOPHYTE 

After  examining  growing  fern  gametophytes,  determine  and 
record  the  following  points  concerning  the  habitat  and  nature 
of  the  gamete-bearing  plant,  or  gametophyte  generation,  of 
the  ferns. : 

1.  Habitat.  AVhat  is  the  natural  habitat  of  these  little  plants 
in  nature  ?  Does,  your  observation  indicate  that  fern 


122         LABORATORY  AND  FIELD  EXERCISES 

gametophytes  are  abundant  iu  their  natural  habitat  ? 
Why  not,  since  ferns  produce  abundant  spores  ? 

2.  Habit.   What  group  of  plants  already  studied  have  game- 

tophytes most  similar  to  those  of  ferns  ?  Is  this  group 
closely  related  to  ferns  ?  What  is  the  most  striking 
difference  between  the  ferns  and  the  Hepaticae  as 
regards  their  gametophyte  and  sporophyte  plants  ? 

3.  Structure.    Wash  the  soil  from  the  underside  of  mature 

gamete  plants.  Determine  the  structure  of  the  plant 
body  and  the  nature  of  the  absorbing  organs. 

4.  Sex  organs. 

a.  Study  the  position  of  the  archegonia  and  antheridia  on 

the  ventral  side  of  the  gametophyte.  Observe  in 
models  and  in  the  text  the  structure  of  these  organs. 
Are  they  essentially  the  same  as  those  in  the  Bry- 
ophyta  ?  How  would  fertilization  be  effected  ?  Is  the 
position  of  these  sex  organs  favorable  for  insuring 
fertilization  ?  Be  able  to  explain. 

b.  If  sections  are  available,  the  student  should  study  sec- 

tions cut  through  the  gametophyte  and  the  sex 
organs  for  a  more  exact  knowledge  of  the  structure 
of  the  archegonia  and  antheridia. 

c.  Development   of  the  gametophyte.    Study   germinating 

spores  which  show  early  stages  in  the  formation  of 
the  gametophyte.  Draw  and  label  stages  observed. 

THE  EMBRYO  AND  THE  LIFE  HISTORY 

1.  Embryo.  Study  young  sporophytes  growing  from  game- 
tophytes. What  are  the  parts  of  the  spore  plant  ?  How 
are  they  attached  to  the  gamete  plant  ?  What  relation 
does  this  young  spore  plant  bear  to  the  adult  sporophyte  ? 
Consult  the  text  figures  on  this  point. 


THE  PLANT  GROUPS  123 

2.  Life  history. 

a.  Construct  a  graphical  life  history  of  the  fern  similar  to 

that  of  Ricciocarpus. 

b.  Contrast  briefly  in  your  notes  the  alternating  genera- 

tions of  the  fern  and  the  bryophyte. 

B.  EQUISETALES  (HORSETAILS) 
SPOROPHYTE 

Compare  the  main  subdivisions  of  the  plant  body  of  some 
species  of  Equisetum  with  that  of  the  true  ferns  as  regards 
both  form  and  function. 

1.  The  plant  body  and  its  plan. 

a.  Main  subdivisions.   Has  the  Equisetum  plant  the  same 

divisions  into  horizontal  rhizome,  aerial  green  leaves, 
and  roots  as  the  true  ferns  ?  What  organs  perform  the 
functions  of  photosynthesis,  absorption,  conduction, 
and  storage  ?  What  portions  would  carry  the  plant 
over  winter  or  extreme  drouth  ?  How  does  Equisetum 
differ  from  ferns  as  regards  the  above  points  ? 

b.  Vegetative  parts.    Is  the  main  stem  segmented  into 

regular  nodes  and  iuternodes  ?  Is  the  leaf-and- 
brauch  arrangement  cyclic  or  spiral  ?  Determine 
the  origin  of  lateral  buds  and  branches  with  refer- 
ence to  the  leaves.  Is  it  the  same  as  in  higher 
plants  ?  Compare  the  aerial  and  underground  stem 
and  lateral  branches  in  these  respects.  Are  they 
all  constructed  on  the  same  plan  ?  Note  any  varia- 
tions that  may  occur.  Observe  the  origin  and  nature 
of  the  roots. 

c.  Strolili,  or  reproductive  cones.   Observe  these  structures 

and  their  position  on  the  plant.  Are  their  parts 
(as  seen  externally)  arranged  on  the  same  plan  as 


124          LABORATORY  AND  FIELD  EXERCISES 

the  leaves  on  the  main  axis,  thus  following  the 
general  body  plan  ?  Is  the  strobilus  placed  in  the 
right  position  on  the  shoot  for  spore  dissemination? 

2.  Adjustments  to  the  environment.    Are  there  the   same 

responses  to  environmental  forces  by  tropisms  in  Equi- 
setum  as  in  ferns  ?  Be  able  to  explain  the  relation 
between  the  responses  of  the  various  organs  and  the 
functions  which  they  perform. 

3.  Drawings.    Make  an  accurate  drawing  of  the  Equisetum 

plant  studied,  to  indicate  the  subdivisions  and  plan  of 
the  plant  body.  Indicate  by  proper  terms  the  responses 
and  adjustments  of  the  various  organs  to  environ- 
mental forces. 

4.  Analysis.    Analyse  one  or  more  species  of  Equisetum  and 

record  analyses  under  family,  genus,  and  species,  as 
in  ferns. 

5.  Habitat  and  habit. 

a.  What  is  the  usual  habitat  of  the  equiseta  ?  Are  there 
variations  in  habitat  ?  Determine  these  points  by 
field  studies  and  by  reference  to  texts  and  analytical 
keys.  Does  the  habitat  of  species  growing  in  ponds 
or  lakes  correspond  to  the  form  and  structure  of 
these  species  ?  How  can  you  explain  the  evident 
discrepancy  between  habitat  and  habit  in  these  cases  ? 

6.  Seasonal   history.     Are   equiseta    annuals,   biennials,  or 

perennials  ?  herbaceous  or  woody  plants  ?  In  what 
form  do  they  pass  the  winter  ?  How  do  they  differ 
from  ferns  in  these  respects  ? 

7.  Summary. 

a.  Summarize  the  distinctive  characteristics  of  equiseta 

which  differentiate  them  from  true  ferns. 

b.  Explain  the  apparent  discrepancy  between  habitat  and 

habit  in  species  growing  in  water. 


THE  PLANT  GROUPS  125 

SUPPLEMENTARY  STUDY 

Equisetum  arvense 
SPOROPHYTE 

1.  Dimorphic  character  of  the  aerial  stems. 

a.  Compare   aerial   vegetative  and    reproductive    shoots  of 

Equisetum  arvense  as  to  body  plan,  lateral  organs,  and 
color.  What  is  the  apparent  advantage  of  this  division 
of  labor  in  aerial  stems  ?  Do  the  reproductive  and  the 
vegetative  shoots  grow  at  the  same  time  of  the  year  ? 
Which  has  the  longer  life  ? 

b.  Construct  a  diagram  to  show  the  relations  of  the  under- 

ground and  the  dimorphic  aerial  portions  of  Equisetum 
arvense.  Label  parts  correctly. 

2.  Structure  and  reproduction. 

a.  Structure.    Cut  thin  sections  across  the  stems  of  Equi- 

setum arvense.    Mount  and  study  with  a  low  power. 

(1)  Locate  the  main  tissue  layers :  namely,  epidermal,  skele- 

tal (or  supporting),  vascular  (or  conducting),  and  stor- 
age tissues.  How  does  the  general  arrangement  of 
tissues  differ  from  that  found  in  the  fern  ?  Can  you 
relate  the  position  of  the  various  tissues  to  their  use, 
or  function,  in  the  plant  body,  —  for  example,  the 
skeletal  and  the  green  tissue  ?  Why  are  both  of 
these  tissues  placed  on  the  outside  of  the  stem  ?  Why 
is  the  vascular  tissue  so  small  in  amount  ?  What  are 
the  advantages  of  the  large  intercellular  spaces  ? 

(2)  Make  an  outline  drawing  (no  cells)  of  your  section 

illustrating  the  position  of  the  various  tissues. 

(3)  Summarize  the  adaptive  features  of  the  structure  of 

the  stem. 

b.  Asexual  reproduction. 

(1)  Compare  the  arrangement  of  the  parts  of  the  stro- 
bilus  of  Equisetum  arvense  with  that  of  the  species 
examined  above  as  to  plan  and  arrangement  of  parts. 


126         LABOKATOKY  AND  FIELD  EXERCISES 

(2)  Bisect  a  strobilus.   What  are  the  parts  of  a  strobilus 

thus  exposed  ?  Is  the  strobilus  a  modified  shoot  ? 
Are  there  nodes,  internodes,  and  lateral  members, 
as  in  the  main  central  axis  ? 

(3)  Sporangiophores  and  sporangia.    The  sporangiophores 

are  the  shield-shaped  lateral  organs  of  the  strobilus 
which  bear  the  sporangia.  They  are  not  true  sporo- 
phylls,  or  modified  leaves.  How  many  sporangia 
are  there  on  a  single  sporangiophore  ?  How  are  they 
arranged  ?  What  is  the  shape  of  a  sporangium  ? 
Dissect  sporangia  out  on  a  slide  to  determine  this 
point.  Can  you  determine  the  mode  of  opening 
in  rather  mature  sporangia?  Draw  sporangia  to 
show  the  line  of  dehiscence. 

(4)  Spores  and  elaters.    Dissect  spores  out  on  a  slide  (let 

them  dry  if  preserved  material  is  used).    Breathe 
on  them  gently.    Result  ?  Study  the  structure  of 
the  spores.    Draw  them.    See  the  text  for  a  descrip- 
tion of  spore  structure.    Label  your  drawing. 
3.  Life  history  and  relationships.    Study  the  life  history  of 
Equisetum  in  the  text. 

a.  Why  are  these  plants  classified  with  the  ferns  under  the 

common  group  Pteridophyta  ? 

b.  In  what  respects  are  the  ferns  and  equiseta  alike  in  their 

life  history  ?    Summarize  your  conclusions  respecting 
a  and  b  in  your  notes. 

C.  LYCOPODIALES  (CLUB  MOSSES)— LYCOPODIUM 
SPOROPHYTE 

1.  The  plan  of  the  plant  body.  Compare  with  that  of  true 
ferns  and  equiseta.  Are  there  characters  concerned 
with  the  central  axis  or  the  lateral  members  (leaves, 
roots,  and  branches)  which  distinguish  lycopods  from 
the  other  Pteridopliyta  already  studied? 


THE  PLANT  GROUPS  127 

2.  Asexual  reproduction. 

a.  Observe  the  strobili  of  a  lycopod  which  is  bearing  spores. 

What  is  the  position  of  the  strobilus  on  the  stem? 
Are  its  parts  of  the  same  general  nature  and  arrange- 
ment as  those  of  the  main  axis? 

b.  Structure  of  strobilus,  sporangia,  and  spores.    Determine 

these  points  by  dissecting  the  leaves,  or  sporophylls, 
from  strobili.  How  is  the  sporangium  related  to  the 
scalelike  leaves  (sporophylls)  which  bear  them  ?  How 
and  where  do  the  sporangia  open  (dehisce)  to  shed 
the  spores  ?  Are  the  spores  numerous  and  all  of  one 
kind,  namely,  homosporous  ? 

c.  Draw  a  single  sporophyll  with  its  sporangium. 

3.  Analysis.    Analyze  two  or  more  species  of  lycopods  and 

record  your  analyses  as  for  ferns  and  equiseta. 

4.  Distinctive  characters.    Summarize  the  characters  which 

seem  to  you  to  distinguish  lycopods  from  other  Pteri- 
dophyta  studied. 

SELAGINELLA 
SPOROPHYTE 

Study  one  or  more  species  of  Selaginella  with  reference 
to  the  following  more  important  and  distinctive  features  of 
these  plants: 

1.  Body  plan  and  adjustment  of  organs  to  the  environment. 
a.  Leaves. 

(1)  Note  their  arrangement  and  adjustment  to  light. 

If  erect  and  creeping  species  are  available,  com- 
pare them  in  these  respects. 

(2)  Note  the  ligule,  a  small  outgrowth  on  the  adaxial  side 

near  the  stem.  This  is  an  ancestral  character  which 
existed  in  the  lycopods  of  early  geologic  periods. 


128          LABORATORY  AND  FIELD  EXERCISES 

b.  Rhizophores  and  roots.  The  rhizophores  are  naked,  stem- 
like  organs  which  Lear  the  roots  at  the  tip,  where 
the  rhizophores  come  in  contact  with  the  soil.  What 


FIG.  24.    Selaginella  martensii 

A,  branch  bearing  cones  and  showing  the  leaf  arrangements ;  B,  inner  face 
of  a  megasporophyll,  showing  the  large  megasporangium  containing  a  group 
of  four  megaspores  (tetrad) ;  C,  two  views  of  megaspores;  I),  inner  face  of  mi- 
cro.sporophyll,  showing  microsporangium ;  E,  microspores ;  F,  diagram  of  a 
longitudinal  section  of  cone,  illustrating  position  of  microsporophylls  and  megaspo- 
rophylls  and  their  microsporangia  and  megasporangia.  From  Bergen  and  Davis's 
"  Principles  of  Botany  " 

would  be  the  function  of  these  rhizophores  in  the 
natural  habitat  of  Selaginella  ?  The  rhizophore  is 
also  an  ancient  organ  which  occurred  in  the  early 
relatives  of  Selaginella. 


THE  PLAXT  GROUPS  129 

c.  Draw  a  portion  of  a  Selaginella  plant  to  illustrate  the 
above  points. 

2.  Asexual  reproduction. 

a.  Strobili.  Do  the  species  of  Selaginella  that  you  are 
examining  bear  distinct  strobili?  What  is  the  nature 
of  the  sporophylls  ?  Do  they  resemble  ordinary 
leaves  in  form  and  color  ?  Why  are  they  called 
sporophylls  ? 

I.  Sporangia  and  spores. 

(1)  Remove  sporophylls  from  different  parts  of  the  stro- 

bilus  and  examine  the  sporangia.  Are  the  sporangia 
all  alike  in  appearance  and  in  the  number  of  spores 
which  they  bear  ?  Dissect  spores  from  several  spo- 
rangia to  determine  this  point.  What  do  you  find? 
Have  we  studied  any  plants  before  which  bore  two 
kinds  of  spores  ?  Do  any  particular  portions  of 
the  strobilus  bear  a  particular  kind  of  sporangium 
and  spore  ? 

(2)  Draw  the  two  kinds  of  sporangia  and  sporophylls 

found  in  the  strobili  that  you  are  examining. 
Draw  the  two  kinds  of  spores.  Eead  the  text 
on  asexual  reproduction  of  Selaginella  and  label 
your  figures  correctly. 

(3)  Study  of  sections.    If  sections  of  strobili  of  Sela- 

ginella are  available,  study  the  relations  of  the 
microsporangia  and  megasporangia  to  the  main 
axis  of  the  strobilus  and  to  the  sporophylls. 
Observe  the  structure  of  the  sporangia  and 
spores.  Draw  and  label  your  figure. 

3.  Life  history.    Study  the  text  figures  and  discussions  con- 

cerning the  gametophytes,  sex  organs,  and  life  history 
of  Selaginella. 

4.  Distinctive  characteristics.    Summarize  the  new  and  dis- 

tinctive characters  of  Selaginella. 


SECTION  IX.   GYMNOSPERMS 

A.  CYC  AD  ALES  (CYC  ADS) 
SPOROPHYTE 

1.  Habitat  and  relationships. 

a.  Consult   the   text   and  assigned   readings    concerning 

the  habitat,  classification,  and  relationships  of  the 
Cycadales.  What  is  the  natural  habitat  of  the 
cycads  in  the  United  States  ?  Were  they  ever  more 
abundant  and  important  as  a  part  of  the  world's 
vegetation  than  they  are  at  the  present  time  ?  What 
position  in  classification  do  they  occupy  among 
living  plants  ?  What  ancestral  relationships  have 
they  which  make  them  important  to  study  in  a 
course  in  plant  evolution  ? 

b.  Summarize  answers   to  the   above  questions  in  your 

notes. 

2.  Habit  and  body  plan. 

a.  What  is  the  body  plan  of  cycads  ?     See  the  arrange- 

ment of  leaf  bases  and  green  leaves  on  the  stem. 
Do  you  know  of  ferns  or  seed  plants  which  the 
cycads  resemble  in  general  habit?  Are  the  cycads 
closely  related  to  such  plants  ? 

b.  Leaves.    Study  young  and  mature   leaves   of  cycads. 

In  what  respects  do  cycad  leaves  resemble  those  of 
ferns  ?  If  leaves  are  unfolding,  notice  the  method 
of  unfolding  of  the  entire  leaf  and  of  the  pinnules. 
If  possible,  note  the  venation  of  leaves  of  Cycas  and 
Zamia,  Are  the  resemblances  of  cycad  leaves  to 
130 


THE  PLANT  GROUPS  131 

those  of  ferns  a  matter  of  chance  or  one  of  blood 
relationship  ? 

c.  Roots.  Are  the  roots  of  cycads  distinctive  ?  If  so,  in 
what  respects  ? 

3.  Asexual  reproduction.    Study  living  or  preserved  material 

or  museum  specimens. 

a.  Strobili.  Determine  the  position  of  strobili  on  the 
main  axis,  the  distribution  of  male  and  female 
strobili  on  the  same  or  on  different  plants,  and  the 
general  nature  of  the  strobili. 

(1)  Are  the  strobili  terminal  or  lateral  in  origin  ?   Are 

the  plants  monoecious  or  dioecious  as  regards  the 
distribution  of  strobili? 

(2)  Are  the  parts  of  the  strobilus  arranged  on  the  same 

plan  as  those  of  the  main  plant  body  ?  To  what 
parts  of  the  plant  body  do  the  main  parts  of  the 
strobilus  correspond  ?  Are  there  sporophylls  and 
a  central  axis  as  in  the  lycopods  and  Selaginellal 
Are  the  sporophylls  cyclic  or  spiral? 

4.  Sporophylls  and  sporangia. 

a.  Microsporophylls,  sporangia,  and  spores. 

(1)  Sporophylls.    Note   the  form   and  relation   of  the 

sporophylls.  Compare  (by  means  of  specimens 
or  figures)  the  sporophylls  of  different  kinds  of 
Cycadales.  Are  any  of  them  leaflike  ?  To  what 
do  these  sporophylls  correspond  in  ferns  ?  in 
Selaginella  and  lycopods  ? 

(2)  Microsporangia.   Are  the  microsporangia  abaxial  or 

adaxial  on  the  sporophyll?  Has  their  position 
any  relation  to  spore-shedding?  Is  there  any 
definite  arrangement  into  sori  ? 

(3)  Spores.    Searcli  for  sporangia  shedding  spores.    Is 

there  a  definite  line  of  dehiscence?    Study  spores 


132         LABORATORY  AND  FIELD  EXERCISES 

and  compare  them  with  those  of  ferns  and 
Selayinella.  Do  cycad  spores  differ  in  structure 
or  in  function  from  those  of  Pteridophyta  ? 
(4)  Drawings.  Draw  the  ventral  (abaxial)  view  of  a 
microsporophyll  and  its  sporangia.  Label.  Draw 
two  or  three  microspores. . 

b.  Megasporophylls  and  sporangia. 

(1)  Eemove   entire   sporophylls   with    their   megaspo- 

raiigia,  or  ovules,  from  the  female  strobili.  Note 
young  or  undeveloped  megasporangia  if  found. 
Are  these  megasporangia,  or  ovules,  similar  to 
the  ovules  of  the  mandrake  and  the  bean  studied 
earlier  in  the  text  ?  Consult  these  earlier  figures 
and  text  descriptions.  If  they  are  the  same,  are 
all  ovules  and  seeds  megasporangia  ? 

(2)  Gross  structure  of  the  megasporangium.    Bisect  the 

megasporangia  of  Zamia  and  study  their  structure 
as  shown  on  the  cut  surface.  Compare  the  Zamia 
megasporangium  with  that  of  the  mandrake.  Do 
you  find  integuments,  micropyle,  and  funiculus 
in  the  megasporangium  of  Zamia  ?  What  fills 
the  center  of  the  sporangium  ?  Do  you  find 
structures  looking  like  archegonia,  or  eggs?  Use 
hand  lens  and  examine  your  specimen  carefully. 

c.  Conclusions.    What  conclusions  do  you  draw  as  to  the 

nature  of  the  megasporangium  and  its  contents  ? 
Does  it  contain  spores  or  structures  belonging  to  a 
gametophyte  generation  ?  Does  the  sporangium  ever 
open  (dehisce)  as  in  the  microsporangia  ?  State  in 
summary  form  your  conclusions  as  to  relation  of 
the  megasporangia  of  Zamia  to  ovules  of  the  man- 
drake, locust,  and  bean  studied  in  Part  I,  and  to 
megasporangia  in  the  heterosporous  Selaginella. 


THE  PLANT  GROUPS  133 

GAMETOPIIYTE 

Study  text  figures  and  descriptions  of  the  megasporangium 
of  Zamia.  With  the  aid  of  such  descriptions  study  your 
specimen  with  a  hand  lens  and  determine  the  relation  of  the 
following  structures  : 

1.  The  integument  layers  and  the  micropyle.    How  do  the 

layers  of  the  integument  differ?  Is  the  micropyle  of 
appreciable  width  ? 

2.  The  pollen  chamber  and  the  remnant  of  the  sporangium. 

Do  you  find  these  structures  in  your  specimen  ?  How 
are  they  related  to  the  gametophyte  and  the  arche- 
gonial  chamber  ? 

3.  The  gametophyte. 

a.  Is  the  gametophyte  of  Zamia  as  large  as  that  of  the 

fern  ?  Has  it  the  same  functions  ?  What  was  the 
source  of  its  food  supply  ?  How  was  this  in  the  fern  ? 
in  Selaginella  ?  Test  the  gametophyte  with  iodine. 
Does  it  contain  reserve  starch? 

b.  Archegoma.    How   many   archegonia   are    there  on   a 

single  gametophyte  of  Zamia  ?  How  do  they  compare 
in  structure  with  the  archegonia  of  Selaginella,  ferns, 
and  mosses  ?  Have  any  structures  common  to  the 
earlier  archegonia  been  lost  ?  Note  the  archegonial 
chamber.  What  is  its  special  function  at  the  time 
of  fertilization  ?  Draw  the  upper  third  of  the  mega- 
sporangium  and  gametophyte  to  bring  out  the  above 
structures.  Label. 

4.  Pollination  and  fertilization.    How  is  pollination  effected 

in  Zamia  1  Is  self-pollination  or  cross-pollination  the 
rule?  How  does  the  pollen  grain  reach  the  pollen 
chamber  ?  What  is  the  function  of  the  pollen  tube  ? 
How  is  fertilization  effected  in  Cycadales  ?  In  what 


134         LABORATORY  AND  FIELD  EXERCISES 

respects  is  the  process  in  cycads  intermediate  between 
that  in  ferns  and  that  in  the  mandrake. 

5.  Structure  of  the  seed.    Study  the  structures  of  the  seed 

in  Zamia  from  specimens  or  from  figures.  Compare  its 
structure  with  that  of  the  mandrake  and  the  pea.  What 
sporophytic  and  gametophytic  structures  are  comprised 
in  the  seed  of  Zamia  ?  If  specimens  are  available,  draw 
a  sectional  view  of  the  cycad  seed  to  show  the  parts  of 
the  embryo  and  the  remaining  structures  of  the  seed. 

6.  Seed  germination.    The   method  of  seed  germination  in 

cycads  is  well  illustrated  by  the  germination  of  the 
acorns,  or  seeds,  of  the  oak.  The  important  things  to 
note  are 

a.  The  structure  of  the  seed  and  embyro. 

b.  The  exit  of  the  embyro  from  the  hard  seed  coat. 

c.  The  function  of  the  cotyledons  and  the  exit  of  the 

plumule. 

d.  The  final  adjustment  of  the  young  plantlet  in  the 

soil  and  air. 

If    the    acorn   is   used,   make   appropriate    drawings    to 
illustrate  stages  a-d. 

7.  Life  history.    Study  the  text  diagrams  in  the  graphical 

life  history  of  Zamia.  Be  able  to  label  and  explain 
each  stage  of  the  life  history  illustrated  in  the  diagram. 

8.  Summary.    Summarize  briefly  the  following  points  relat- 

ing to  the  structure  and  reproduction  of  Zamia  and 
the  Cycadales. 

a.  Summarize   the    fernlike    characteristics    of  Cycadales 

which  indicate  their  pteridophyte  ancestry. 

b.  Summarize  their  new  gymnosperm  characters. 

c.  Give  briefly  the  characteristics  in  which  Cycadales  are 

intermediate  between  PteridopJiyta  and  the  higher 
seed  plants. 


THE  PLANT  GROUPS  135 

B.  CONIFERALES  (CONE-BEARERS).    SPRUCE  AND  PINE 
SPOROPHYTE 

1.  Habitat  (Field  study). 

a.  What  is  the  nature  of  the  habitat  of  the  spruces  and 
pines  of  your  region  as  regards  soil,  drainage,  and 
climate  ?  Do  they  grow  best  on  lowlands  or  on  well- 
drained  slopes  and  uplands?  What  is  the  distribu- 
tion of  spruces  and  pines  in  the  United  States  ?  What 
is  their  natural  habitat  as  regards  soil  and  climate  ? 
Are  they  mesophytic  or  xerophytic  in  general  habit  ? 
How  do  you  explain  the  apparent  discrepancy  between 
habitat  and  habit  in  these  trees  ?  Consult  manuals 
and  assigned  readings  011  the  above  points. 

I.  Summarize  the  above  points  in  your  notes  under  habitat, 
including  geographical  distribution  and  habit. 

2.  Habit. 

a.  Form  and  body  plan  of  the  spruce  and  pine  trees.  Eeview 

the  text  discussion  in  Part  I  on  the  body  plan  and 
mode  of  growth  of  the  spruce  and  pine  trees.  Be  able 
to  account  for  the  erect  conical  form,  the  excurrent 
trunk,  and  the  false  whorls  of  branches  of  spruces 
and  pines.  Why  is  the  trunk  excurrent  ?  What  de- 
termines the  conelike  form  of  the  entire  tree  ?  How 
do  the  false  whorls  arise  ?  Is  the  entire  leafage  well 
exposed  to  light  ? 

b.  Summarize  the  above  points  under  Habit  in  terms  of 

body  plan,  methods  of  growth  of  buds  and  branches, 
and  tropistic  responses  of  leaves  and  branches. 
For  a  general  discussion  of  the  habitat,  distribution,  and  com- 
mercial importance  of  the  spruces  and  pines  the  student  should 
consult  the  text  and  figures  under  Gymnosperms  in  Part  III 
of  text.    See  also  the  general  map  of    forest  areas  (Fig.  223). 


136          LABORATORY  AKD  FIELD  EXERCISES 
ANATOMY  OF  THE  SPRUCE  STEM 

TRANSVERSE  SECTIONS 

Cut  thin  transverse  sections  from  living  spruce  twigs  about 
one  eighth  of  an  inch  in  diameter.  Mount  some  sections  in 
alcohol  and  some  in  iodine  solution.  Observe  the  latter  sections 
for  starch  storage,  wood  rays,  pith,  etc. 

1.  The  main  tissue  layers  of  the  spruce. 

a.  Compare  the  tissue  layers  of  the  spruce  with  those  of 

the  lilac  and  fern.  Which  stem  does  the  spruce  most 
nearly  resemble  in  structure  ?  Does  the  spruce  pos- 
sess both  a  cork  cambium  and  the  cambium  which 
forms  phloem  and  xylem  ?  Note  carefully  the  rela- 
tions of  corky  bark,  green  cortex,  phloem,  cambium, 
xylem,  and  pith. 

b.  Leaf  gaps  and  traces.  Observe  the  shape  of  the  pith. 

Do  you  find  lobes  of  the  pith  (leaf  gaps)  extending 
into  the  xylem  ?  If  so,  note  their  extent  and  the 
nature  of  the  xylem  ring  opposite  them.  Leaf  traces, 
•looking  like  wide  wood  rays,  often  appear  opposite 
these  pith  lobes  or  leaf  gaps  in  the  spruce.  Consult 
the  text  figures. 

c.  Observe  sections  stained  with  iodine  for  starch-storage 

areas.  Where  is  starch  stored  in  the  spruce  ? 

d.  Make  an  accurate  drawing  of  your  section  in  outline 

(no  cells),  indicating  the  main  tissue  areas  and  their 
limits.  Include  wood  rays,  annual  rings,  leaf  gaps, 
and  leaf  traces.  Study  the  text  and  label  your 
drawing  accurately. 

e.  Summary.  Write  an  accurate  and  concise  summary  of 

the  structure  of  the  spruce  stem  in  the  form  indicated 
for  herbaceous  dicotyledons  and  for  the  fern.  Indicate 


THE  PLANT  GROUPS  137 

in  the  summary  the  particulars  in  which  the  spruce 
stem  resembles  that  of  the  fern,  and  the  significance 
of  this  resemblance.  Consult  the  text  on  the  structure 
of  the  spruce  stem. 

2.  Structure  of  the  tissues  (prepared  slides).  Observe  with 
low  and  high  powers  of  the  microscope  the  tissue  layers 
and  tissue  elements  in  stained  preparations  of  spruce 
stems. 

a.  The  cork  lark.  Of  what  kinds  of  tissue  is  it  composed  ? 

Is  there  an  apparent  tendency  to  form  separating 
scales  ?  Are  the  cells  of  the  cork  bark  living  or 
lifeless  ?  The  cork  cambium  forms  an  inner  layer  of 
rectangular  living  cells  on  the  inner  side  of  the  cork 
layers  in  the  spruce. 

b.  Cortex.  Observe  the  character  of  its  cells  and  the  struc- 

ture of  the  large  resin  canals  with  a  lining  layer  of 
small  resin  secreting  cells. 

c.  Phloem  and  cambium.  Can  you  differentiate  the  phloem 

and  cambium  layers  ?  Does  the  phloem  show  annual 
growth  layers  corresponding  to  those  of  the  xylem  ? 
What  marks  the  outer  boundary  of  each  annual  layer 
of  phloem  (this  outer  limit  of  the  phloem  can  be 
determined  by  the  outer  limit  of  the  wood  rays)  ? 

d.  Xylem. 

(1)  Annual  rings,  composed  of  spring  and  summer  wood. 
Compare  these  with  similar  structures  of  woody 
dicotyledons.  How  do  the  tissue  elements  of  the 
spring  and  summer  wood  differ  in  the  spruce 
from  similar  structures  in  lilac  and  alder  ?  Which 
kind  of  wood  is  better  adapted  for  rapid  water 
conduction  ?  Is  the  wood  structure  adapted  to 
the  leaf  structure  and  transpiration  requirements 
in  the  spruce  ? 


138         LABORATORY  AND  FIELD  EXERCISES 

(2)  Storage  tissues  of  the  xylem.  Is  the  spruce  as  well 

provided  with  storage  tissues  as  the  above- 
mentioned  stems  ?  How  does  it  compare  with 
the  storage  system  of  the  fern  stem  ?  Is  the 
spruce  intermediate  in  this  respect  between 
the  alder  and  the  fern  ?  Be  able  to  explain. 

(3)  Drawings.  Outline  a  sector  of  a  transverse  section 

of  the  spruce  stem.  Detail  in  this  sector  the  cork 
layer,  a  small  portion  of  the  xylem  at  the  junction 
of  two  annual  rings,  a  leaf  gap,  and  a  leaf  trace. 

LONG  SECTIONS 

Study  thin  sections  cut  from  spruce  or  pine  to  determine  the 
structure  of  the  water-carrying  tracheids  and  of  the  wood  rays. 
Mount  in  alcohol  if  freshly  prepared  material  is  used. 

1.  Tracheids.  What  is  the  nature  of  the  conducting  elements, 

or  tracheids,  making  up  the  wood  of  pine  or  spruce  ? 
Are  they  single  cells  ?  What  is  their  shape  ?  What  are 
their  surface  markings  ?  How  do  they  differ  from  the 
vessels,  or  trachea?,  of  the  higher  plants  studied  earlier 
in  the  course  ?  Compare  the  ducts  of  the  lilac  and  alder 
with  the  tracheids  in  your  slide.  Do  the  wall  mark- 
ings of  tracheids  differ  from  those  of  ducts  ?  Study  the 
bordered  pits  on  the  walls  of  the  tracheids,  consulting 
the  text  concerning  their  structure.  On  which  walls 
of  the  tracheids  are  the  bordered  pits,  the  tangential 
walls  or  the  radial  walls  ? 

2.  Wood  rays.    If  rays  are  seen  in  radial  sections,  note  the 

differentiation  of  their  cells  into  living  starch-bearing 
cells  and  dead  water-conducting  tracheids. 

3.  Drawings.  Draw  a  small  portion  of  your  section  accurately 

to  show  the  structure  of  tracheids  and  wood  rays. 


THE  PLANT  GROUPS  139 

ASEXUAL  REPRODUCTION 

1.  Ovulate  strobili  of  the  spruce.    Study  surface  views  of 

mature   dry   strobili   of  the   spruce  and   median  long 
sections  of  preserved  strobili. 
a.  Gross  parts. 

(1)  Are  the  parts  of  the  spruce  strobilus  the  same  as 

those  of  strobili  in  lycopods  and  cycads  ?  Are 
there  sporophylls  ?  a  central  axis  ?  ovules  or 
megasporangia  ?  Is  the  strobilus  cyclic  or  spiral 
in  plan  ?  Study  both  surface  and  sectional  views 
of  the  strobilus  to  determine  the  above  points. 

(2)  Seeds.  Do  you  find  seeds  or  ripened  megasporangia 

in  the  mature  strobili?  How  are  they  adapted 
to  dissemination? 

(3)  Drawings.    Draw  surface  and  sectional  views  of 

portions  of  the  strobilus  about  one  inch  in 
length.  Draw  the  median  section  very  accu- 
rately. Label  the  parts  in  terms  of  sporophylls 
and  sporangia. 

1.  Megasporopliyll,  sporangium,  and  bract.  Piemove  sporo- 
phylls from  strobili  and  determine  the  relations  of 
the  above  structures.  Construct  a  vertical  sectional 
view  of  bract,  megasporophyll,  and  megasporangium. 
Consult  the  text  concerning  the  morphology  of  the 
spruce  strobilus.  Is  it  a  simple  strobilus  like  that  of 
the  lycopod  or  is  it  a  branch  system  with  bracts 
corresponding  to  regular  leaves  ?  To  what  do  the  cone 
scales  correspond  ? 

2.  Staminate  strobili. 

a.  Gross  parts.  Have  the  staminate  strobili  the  same  parts, 
with  a  similar  arrangement,  as  the  ovuliferous  strobili? 
Have  they  both  bracts  and  sporophylls  ? 


140          LABORATORY  AND  FIELD  EXERCISES 

b.  Sporangia,  Are  the  inicrosporangia  abaxial  or  adaxial  ? 

How  many  sporangia  are  there  on  a  sporophyll  ? 
Determine  the  mode  of  dehiscence  in  mature  spo- 
rangia. Is  the  abaxial  position  an  advantage  in  the 
dissemination  of  spores  ?  Note  the  growth  in  length 
of  the  internodes  of  the  strobilus  when  the  micro- 
spores  are  ready  for  dissemination. 

c.  Microspores.  Study  the    structure    of   the  microspores. 

How  is  it  adapted  to  dissemination  ? 

d.  Drawings.    Draw  an  abaxial  view  of  a  microsporophyll 

with  its  sporangia.    Draw  a  microspore. 
3.  Pollination,  fertilization,  and  carpotropic  movements.    If 
material   is  available,  study  young   pine   and    spruce 
cones  at  the  pollination  stage. 

a.  Pollination.  What  is  the  position  of  the  strobilus  at  this 

stage  ?    What  is  the  position  of  the  sporophylls  ? 

b.  Fertilization.    Compare   the   size   and   position   of  the 

strobili  at  pollination  with  that  of  similar  strobili 
at  the  time  of  fertilization  and  seed-shedding.  Note 
the  changes  in  position  of  the  strobili  due  to  carpo- 
tropic movements  after  pollination  is  effected.  Com- 
pare the  pine  and  the  spruce  in  these  respects. 

c.  Make  outline  sketches  to  illustrate  changes  in  the  size 

and  position  of  pine  or  spruce  strobili  at  the  polli- 
nation, fertilization,  and  fruiting  stages. 

GAMETOPIIYTES 

1.  Male  gametophyte.  Study  the  structure  of  the  microspore 

and  of  the  male  gametophyte  from  prepared  slides. 
a.  TJie  microspore.    How  does  the  microspore  differ  in 
structure  from  an  ordinary  cell  ?    Note  the  charac- 
ter of  the  cell  wall,  nucleus,  and  cytoplasm.    Draw 
a  microspore  in  section. 


THE  PLANT  GKOUPS  141 

b.  Crametophyte.    Study    the   structures    within   a  germi- 

nated microspore.  Do  you  find  the  two-celled  male 
gametophyte  ?  the  generative  cell  ?  If  possible,  find 
specimens  in  which  the  generative  cell  has  formed 
a  stalk  cell  and  a  body  cell. 

c.  Comparisons.    Compare  the  above  structures  with  the 

male  gametophyte  and  antheridia  of  Selaginella  and 
cycads.  What  structures  have  been  lost  ?  Why  are 
the  lost  structures  not  necessary  in  pine  or  spruce  ? 
To  what  in  the  germinated  microspore  of  Selaginella 
do  the  generative  cell  and  the  stalk  cell  of  the  spruce 
correspond  ? 

d.  Draw  a  germinated  microspore  and  male  gametophyte 

of  the  pine  or  spruce.  Summarize  answers  to  ques- 
tions under  c. 

Female  gametophyte.  Study  median  long  sections  of 
megasporangia  in  which  the  female  gametophyte  has 
formed.  Study  the  section  with  hand  lens  and  low 
power,  comparing  it  with  similar  sections  of  cycad 
megasporangia. 

a.  Megasporangium.    What  structures  of  the  old  megaspo- 

raugium  are  found  in  the  section  you  are  studying? 
Are  there  integuments,  a  micropyle,  and  sporangial 
tissue  proper  ?  Do  they  have  the  same  relation  to 
each  other  as  in  the  cycad  ?  Is  there  a  distinct 
pollen  chamber  ? 

b.  G-ametopliyte.    Study  the  gametophyte  tissue,  the  arche- 

gonia,  and  the  gametes.  What  is  the  nature  of  the 
gametophyte  tissue  ?  What  is  the  structure  of  the 
archegonia  ?  Have  they  protective  wall  cells  con- 
sisting of  neck  and  venter  ?  How  many  of  the  usual 
central  cells  (namely,  neck  canal  cells,  ventral  canal 
cells,  and  gamete  cells)  are  there  ? 


142         LABORATORY  AND  FIELD  EXERCISES 

c.  Comparisons.    How  does  the  gametophyte  of  the  spruce 

compare  with  those  of  the  cycads  ?  Has  there  been 
any  further  reduction  in  the  archegonia  ? 

d.  Draw  your  section  and  label  its  parts  correctly.   Draw 

a  single  archegonium  enlarged.    Label. 

3.  The  seed  and  embryo. 

a.  Cut  median  long  sections  of  seeds  of  pine  or  spruce 

which  have  been  softened  in  water.  Study  the  sec- 
tion of  the  seed  which  shows  the  embryo  most  plainly. 

b.  Seed  structure.   Compare  the  structure  of  the  seed  with 

that  of  the  ovules  just  studied.  What  structures  of 
the  ovule  remain  in  the  seed  ?  What  structures  are 
changed  ?  From  what  did  the  embryo  arise  ? 

c.  Embryo  structure.  Compare  the  structure  of  the  embryo 

with  that  of  seeds  previously  studied.  Do  you  find 
hypocotyl  and  cotyledons  ? 

d.  Draw  your  section  and  label  the  parts  of  both  seed 

and  embryo. 

4.  Seed  germination.    Study  seeds  in  process  of  germination 

and  make  sketches  to  illustrate  these  phenomena: 

a.  Exit  of  the  embryo  from  the  seed.    What  part  of  the 

embryo  emerges  from  the  seed  first  ?  Do  any  parts 
remain  in  the  seed  ? 

b.  Exit  of  the  embryo  from  the  soil.    How  is  this  effected 

and  by  what  parts  of  the  embryo  ?  Compare  this 
stage  with  a  similar  stage  in  peas  illustrated  in 
Part  I  of  the  text. 

c.  Adjustment  of  the  embryo  to  light  and  soil.    Compare 

with  peas  as  above. 

d.  Make  appropriate  drawings  to  illustrate  a,  b,  c,  above. 

5.  Life  history.    Write  a  graphical  life  history  of  the  spruce, 

indicating  the  main   stages   of  the  gametophyte  and 
sporophyte  generations. 


SECTION  X.  ANGIOSPERMS  (DICOTYLEDONS) 

SPOROPHYTE 

Examine  typical  dicotyledons  in  the  laboratory  and  in  the 
field,  and  review  previous  work  on  dicotyledons  such  as  beans, 
mandrake,  locust,  and  elm.  Determine  as  follows  the  distinc- 
tive characteristics  of  dicotyledons  which  distinguish  them 
from  Pteridophyta  and  gymnosperms. 

1.  Habitat.    What   is   the   prevailing  habitat   of    dicotyle- 

donous plants  of  your  region  ?  Be  able  to  name  some 
mesophytes,  xerophytes,  and  hydrophytes  among  them. 
Is  your  region  typical  for  the  habitat  of  dicotyledons  in 
the  United  States  ?  Consult  the  text  under  Descriptive 
Terms  for  figures  and  the  meaning  of  terms  used  below. 

2.  Habit  (geranium  and  similar  dicotyledons). 
a.  Leaf  form  and  venation. 

(1)  Compare   the   leaves   of    dicotyledons   with    those 

of  Pteridophyta  and  gymnosperms,  including 
spruces  and  pines.  Are  the  dicotyledons  large 
leaved  as  a  group  ?  What  terms  describe  the 
form,  margin,  apex,  and  base  of  the  leaves  you 
are  examining?  Consult  Fig.  208  of  text. 

(2)  Hold  a  leaf  toward  the  light  and  study  the  venation. 

Is  it  pinnately  or  palmately  veined  ?  Do  the  veins 
end  free  in  the  margin  (open  venation)  or  are 
they  united  (closed  venation)  ?  See  text,  p.  415. 

(3)  /Structure.    Review  the  structure  of  leaves  in  Chap- 

ter VI  of  the  text  in  connection  witli  Fig.  208. 

3.  Anatomy  (herbaceous  type,  for  example,  geranium).    Re- 

view the  structure  of  herbaceous  stems  in  Part  I  of 
143 


144          LABORATORY  AXD  FIELD  EXERCISES 

the  text.  Cut  thin  transverse  sections  of  young  and 
mature  portions  of  stems  of  any  cultivated  geranium  or 
of  a  similar  herbaceous  stem. 

a.  General  features.   Do  the  stem  sections  of  the  geranium 

correspond  to  the  summary  of  the  herbaceous  stem 
structure  of  Salvia  ?  Do  you  find  tissue  layers  in 
the  stem  sections  of  geranium  not  present  in  Salviai. 
If  so,  what  are  they  and  in  what  main  tissue  zone 
do  they  occur,  epidermis,  cortex,  vascular  cylinder, 
or  pith  ? 

b.  Secondary  growth    by   cambiums.    Compare   transverse 

sections  cut  from  young  and  mature  portions  of  the 
stem  of  a  geranium.  What  differences  do  you  find 
between  the  young  and  the  mature  stem  sections  ? 
Locate  both  the  cork  and  the  vascular  cambiums, 
and  the  secondary  tissues  produced  by  them.  Does 
the  geranium  plant  produce  corky  bark  ?  Examine 
both  the  sections  and  the  surface  of  old  portions  of 
geranium  plants  concerning  this  point. 

c.  Leaf  gaps  and  leaf  traces.   Study  sections  cut  through  a 

node  or  just  below  it.  Do  you  find  interruptions,  or 
gaps,  in  the  vascular  cylinder  where  the  leaf  trace 
is  given  off  ?  Large  branch  gaps  may  also  be  found, 
caused  by  an  outgoing  branch.  Do  you  think  that 
the  irregular  contour  of  the  vascular  ring  is  caused 
in  part  by  leaf  gaps  and  branch  gaps  ? 

d.  Tissues  of  the  vascular  ring.    Compare  these  with  those 

of  the  spruce  just  studied.  Do  you  find  wood  rays? 
annual-growth  rings  ?  wood  parenchyma  ?  Compare 
the  ducts  with  the  tracheids  of  spruce. 

e.  Storage  tissues  of  lite  gerctnhtm   stem.    Determine  the 

places  where  starch  is  stored  in  sections  treated 
with  iodine. 


THE  PLANT  GROUPS  145 

f.  Drawings. 

(1)  Construct  outline  drawings  of  sectors  of  the  young 

and  old  stems  of  geranium. 

(2)  Detail  the  cork  cambium  and  its  products. 

(3)  Detail  a  small  portion  of  the  vascular  cylinder  of  a 

section  of  the  older  portion  of  the  stem. 

g.  Long  sections.   If  long  sections  of  geranium  are  avail- 

able, study  the  tissue  of  the  xylem,  noting  especially 
the  structure  of  the  ducts.  Draw  spiral  and  dotted 
ducts  and  adjacent  tissues. 

SUMMARY 

Summarize  the  structure  of  the  geranium  stem,  modifying  the 
summary  given  for  Sal  via  (p.  108  of  text),  as  you  think  it  should 
be,  to  characterize  the  primary  structure  and  secondary  growth 
of  a  geranium  stem. 

WOODY  TYPE  (ANATOMY) 

1.  Review  the  work  previously  done  on  the  structure  and 
growth  of  trees  in  Part  I  of  the  text  (Fig.  55  and 
discussion). 

a.  Comparisons.  In  what  respects  is  the  woody  dicotyle- 

don better  equipped  for  conducting  water  and  for  stor- 
ing food  than  the  spruces  and  pines  ?  In  what  respects 
does  it  differ  from  the  herbaceous  dicotyledon  ? 

b.  Summarize  the  distinctive  features  of  the  woody  dicoty- 

ledon which  characterize  it  as  the  most  highly 
organized  living  plant.  How  is  it  adapted  structur- 
ally to  perform  the  functions  of  support,  storage,  and 
conduction  ?  Where  are  the  supporting,  storage,  and 
conducting  tissues  located  in  trees  and  shrubs? 
How  do  they  differ  in  this  respect  from  herbs  like 
Salvia  and  geranium  ? 


146          LABORATORY  AND  FIELD  EXERCISES 

REPRODUCTION 

1.  The  flower  and  its  parts.  Consult  the  text  under  repro- 
duction and  review  the  floral  parts  outlined  in  Part  I. 
See  also  Descriptive  Terms,  at  the  beginning  of  Part  III 
of  the  text. 

a.  Structure  of  the  flower.  Determine  which  of  the  follow- 
ing terms  apply  to  the  flower  you  are  studying.  These 
terms  are  denned  under  Descriptive  Terms,  Part  III 
of  the  text. 

(1)  Is  the  flower  you  are  studying  hypogynous,  perigy- 

nous,  or  epigynous  ?  Is  it  perfect,  imperfect,  com- 
plete, or  incomplete  ?  Is  it  regular  or  irregular  ? 

(2)  Are  its  parts  arranged  in  spiral  or  cyclic  form  ?  How 

many  parts  are  there  in  each  set  of  protective  and 
essential  organs  ?  What  is  the  floral  plan  ? 

(3)  Construct   a   ground   plan   of   the   flower.    Record 

the  answers  to  questions  asked  above  under  (1) 
and  (2). 

(4)  The  flower  as  modified  strobilus.  Bisect  the  flower 

and  receptacle  vertically,  and  note  the  arrange- 
ment of  its  parts  on  the  receptacle.  Does  the 
flower  correspond  to  a  strobilus  in  the  nature 
and  arrangement  of  its  parts  ?  Compare  with 
strobili  of  spruce.  To  what  does  the  receptacle 
of  the  flower  correspond  in  a  strobilus  ?  To  what 
do  the  stamens,  pistil,  and  perianth  correspond  ? 
What  are  the  ovules  and  the  anthers  morpho- 
logically ?  What  fundamental  differences  exist 
between  the  strobili  of  the  spruce  and  the  flower 
you  are  examining?  What  new  structures  are 
found  in  flowers  of  the  angiosperms  as  compared 
with  the  strobili  of  gymnosperms. 


THE  PLANT  GROUPS 


147 


(5)  Summary.     Summarize  in  terms  of  axis,  perianth, 

sporophylls,  and  sporangia  the  similarities  and 
differences  between  the  strobili  of  the  spruce  and 
the  flower  you  are  examining. 

(6)  Definition.    Write  a  definition  of  a  flower,  consid- 

ering the  above  facts  concerning  its  morphology. 


FIG.  25.   The  lily  (Lilium  philadelphicum) 

A,  dissected  flower,  showing  the  pistil  and  stamens:  p,  parts  of  the  perianth 
which  have  been  cut  away;  s,  bases  of  stamens  cut  off.  J5,  floral  diagram: 
p,  perianth,  composed  of  two  circles  of  similar  and  petal-like  parts;  s,  stamens, 
likewise  in  two  circles ;  section  of  ovule  case  (ovary)  shown  in  the  center,  com- 
posed of  three  carpels  (c)  so  united  as  to  form  three  locules  containing  the 
ovules.  From  Bergen  and  Davis's  "Principles  of  Botany" 

(7)  Drawings.  Draw  a  vertical  long  section  of  the 
flower  and  label  the  parts  with  terms  corre- 
sponding to  those  used  for  strobili  of  Selaginella, 
cycads,  and  spruce.  Draw  a  ground  plan  of  the 
flower  (Fig.  217  of  text). 


148         LABORATORY  AND  FIELD  EXERCISES 

b.  Morphology  and  structure  of  stamens.  Study  the  struc- 

ture and  mode  of  dehiscence  of  the  anther.  To  what 
do  the  filament  and  anther  correspond  in  the  fern, 
in  Selaginella,  and  in  the  spruce?  Draw  and  label 
the  parts  of  the  stamen  in  terms  of  sporophyll  and 
sporangia. 

c.  Microsporangia.  Study  transverse  sections  of  anthers 

of  the  buttercup,  mandrake,  or  a  similar  dicotyledon. 

(1)  Sporogenesis.  How  many  microsporangia  are  seen 

in  a  transverse  section  of  a  young  anther  ?  Where 
is  the  sporophyll  tissue  'and  how  is  it  differen- 
tiated ?  Is  there  a  supplying  vascular  bundle  and 
surrounding  cortex  and  epidermis  ?  Do  the  spo- 
rangia have  the  same  general  tissues  as  sporangia 
of  ferns  and  microsporangia  of  Selaginella,  cycads, 
and  spruce  ?  Are  there  wall  cells,  tapetum,  and 
sporogenous  cells,  or  spore  mother  cells,  in  each 
microsporangiurn  of  an  anther  ?  Note  carefully  the 
cell  structure,  including  cytoplasm,  nucleus,  and 
chromatin,  of  the  cells  in  each  of  these  layers. 

(2)  Drawing.    Outline  the  entire  section.    Detail  the 

cellular  structure  of  one  microsporangium,  show- 
ing the  cells  of  the  tapetum  and  the  sporogenous 
cells  magnified.  Label  correctly  in  terms  usually 
applied  to  microsporophylls  and  microsporangia. 

(3)  Spore  dissemination.    Study  transverse  sections  of 

mature  anthers.  What  changes  have  occurred  in 
the  microsporangia  during  sporogenesis  ?  How 
many  microsporangia  unite  to  form  one  anther 
sac  ?  How  is  dehiscence  provided  for  ?  Study  the 
wall  cells  of  the  anther  sacs.  Is  the  layer  beneath 
the  epidermis  structurally  adapted  for  opening 
the  anther  sacs  for  spore  dissemination  ?  What 


THE  PLANT  GROUPS  149 

is  the  structure  of  these  cells  and  how  would 
they  work  in  opening  and  closing  the  anther  sacs  ? 
(4)  Microspores.  Xote  the  structure  of  the  microspores 
or  pollen  grains.   What  is  the  nature  of  the  outer 
wall,  or  extine  ?  Outline  one  half  of  your  section 
and  detail  the  cell  structure  of  wall  cells  and 
microspores    on    a    part    of    the    section.    Label 
correctly. 
d.  Pistil  and  fruit. 

(1)  Study  the  pistil,  noting  particularly  the  nature  and 

extent  of  the  ovary,  style,  and  stigmatic  surface. 
Is  each  pistil  simple  or  compound  ?  Observe  the 
megasporangium,  or  ovule,  best  seen  in  mature 
fruiting  pistils.  Compare*  the  megasporophyll 
and  sporangium  with  that  of  Caltha  in  the  text. 

(2)  Drawing.  Draw  the  pistil  so  as  to  show  the  stigmatic 

surface  magnified  and  the  relation  of  megasporo- 
phyll and  megasporangium. 

(3)  Fruit.  Make  a  drawing  to  illustrate  the  nature  and 

parts  of  the  fruit. 

CAP  SELL  A   (SHEPHERD'S  PURSE) 

Study  the  flower  and  inflorescence  of  the  shepherd's  purse  as 
outlined  above  under  Reproduction,  1,  a  (see  Fig.  251,  p.  400, 
of  text).  Make  the  following  special  study  of  pistil,  megaspo- 
rangium, megaspore,  and  embryo  sporophyte.  Consult  the  text 
discussion  of  Capsella  (p.  345  of  text,  and  Fig.  203). 
1.  Pistil. 

a.  Study  young  and  mature  pistils  on  the  inflorescence 
of  Capsella  and  determine  the  relation  of  stigma, 
style  (if  present),  and  ovary.  Is  the  ovary  simple 
or  compound  ?  How  many  placentae  are  there  and 


160         LABOR  A  TOE  Y  AND  FIELD  EXERCISES 

how  many  rows  of  ovules  or  megasporangia  ?  Deter- 
mine this  point  by  gross  studies  of  the  external 
features  of  the  pistil,  and  by  examining  gross  trans- 
verse sections  of  the  pistil  made  with  a  scalpel  or 
safety-razor  blade. 

b.  Draw  a  lateral  view  of  the  pistil  and  a  transverse  section 
of  the  ovary.  Label  the  parts  in  terms  of  megasporo- 
phylls  (carpels)  and  megasporangia  (ovules). 

2.  Megasporangia,   or    ovules.    Dissect  out  a  considerable 

number  of  ovules  from  both  young  and  mature  ovaries 
on  a  slide  in  a  drop  of  water.  Eemove  half  of  the 
ovules  to  a  second  slide  and  mount  in  a  weak  potash 
solution.  Cover  and  study  your  two  preparations  to 
determine  the  following  points : 

a.  Parts  of  the  meyasporangium,  or  ovule.    Observe  the 

funiculus,  ovule  proper,  integuments,  and  micropyle. 
The  embryo  sac  may  often  be  seen  in  outline  in 
specimens  treated  with  potash.  Compare  the  form 
of  young  and  mature  sporangia  and  note  the  gradual 
curvature  of  the  entire  sporangium  and  spore  as  the 
ovule  matures. 

b.  Embryo  sporophyte.   The  embryo  can  often  be  seen,  in 

specimens  bleached  in  potash,  lying  above  the  micro- 
pyle. It  may  be  obtained  free  on  the  slide  by  slight 
pressure  on  the  cover  glass. 

c.  Drawings.    Draw  the  ovules  of   Capsella  to  show  as 

many  of  the  above  structures  as  you  have  been  able 
to  demonstrate,  including  the  embryo  and  its  parts. 
Name  all  parts  correctly,  consulting  the  text  figure 
and  the  description  of  parts  there  represented. 

3.  Female  gametophyte  and  sporophyte  of  Capsella.    Study 

the  female  gametophyte,  embryo  sac,  and  sporophyte 
in  prepared  slides  of  ovaries  of  Capsella.  Work  out  as 


THE  PLA^T  GftOUPS  151 

far  as  possible  the  cellular  structure  and  relations  of  the 
following  structures : 
a.  Megas2)orangia  and  female  gametophyte. 

(1)  If  sections  are  available,  study  the  female  gameto- 

phyte, consisting  of  the  egg  apparatus,  polar  nuclei, 
and  antipodal  cells.  If  such  slides  are  not  avail- 
able, read  the  history  of  the  development  of  the 
megaspores  in  angiosperms  in  the  text  and  com- 
pare the  history  with  that  of  megaspores  in 
Selaginella  and  the  spruce. 

(2)  Drawing.    If  sections  are  studied,  draw  and  label 

the  parts  of  the  megasporangium,  embryo  sac, 
and  gametophyte  cells. 


PART  III.   THE  SPRING  FLORA 


SECTION  XI.   FIELD  WORK  (DICOTYLEDONS) 

A.    TREES  AND  SHRUBS 
A  METHOD  OF  RECORDING  FIELD  OBSERVATIONS 

In  the  following  outline  for  the  study  of  trees  in  the  field 
the  same  general  plan  is  followed  as  in  the  description  of  typi- 
cal species  of  willows,  oaks,  and  maples  in  the  text. 

The  directions  should  usually  be  followed  for  the  study  of 
one  typical  species  in  each  family  until  the  student  is  familiar 
with  the  methods  employed  in  such  work.  Additional  species 
should  then  be  worked  out  by  the  students  independently. 

A  convenient  form  for  recording  field  observations  and  labo- 
ratory studies  on  trees  and  shrubs  is  submitted  below  in  the 
form  of  what  are  termed  Species  Eecord  and  Family  Record. 
If  this  plan  is  adopted,  the  record  of  the  initial  species  studied 
in  each  family  should  be  entered,  as  indicated  in  the  outline, 
by  checking,  in  the  blank  spaces  following  the  terms  employed, 
each  term,  or  character,  that  applies  to  the  species  being 
studied.  Outline  sketches  should  also  be  made  after  such  a 
plan  as  that  indicated  under  Figs.  10,  11,  and  12,  pages  20~23, 
of  text.  See  also  the  figure  of  the  Carolina  poplar  (Populus 
deUoides)  (Fig.  26). 

It  is  convenient  for  class  use  to  have  the  Species  Record 
(p.  156)  and  the  outline  for  Figures  (p.  157)  printed  on  two 
sides  of  a  single  field  sheet.  These  field  sheets  can  then  be  given 
to  each  member  of  the  class  for  recording  the  results  of  field 
and  laboratory  work.  The  Family  Record  (p.  158)  can  be  used 
in  a  similar  manner,  the  outline  for  several  species  being  printed 
on  one  sheet  with  the  familv  characteristics  at  the  end. 


156         LABORATORY  AND  FIELD  EXERCISES 

SPECIES  RECORD 
I.  ANALYSIS 

Family... 

Scientific  name 

Common  name ... 


II.  CHARACTERISTICS 

fa.  Local:  mesophytic xerophytic hydrophytic. 

t:  U  Geographical 

2.  Habit:  erect spreading large: small medium __ 

a.  Bark :  color,  smooth,  flaky,  furrowed,  etc. 

(1)  Trunk 

(2)  Branches . 

b.  Twigs  :  color stout slender smooth hairy.. 

c.  Buds :  size,  color,  smooth,  hairy,  resinous,  etc. 

(1)  Terminal 

(2)  Lateral 

d.  Leaf:  form margin size phyllotfixy 

simple compound netted parallel pinnate 

palmate leaf  scar 

e.  Lenticels:  color shape size Drawing 

3.  Reproduction 

a.  Inflorescence  :  determinate indeterminate kind 

b.  Flower  characters:   hypogynous perigynous epigynous.. 

perfect imperfect regular irregular complete... 

incomplete 

c.  Pollination  features 

(1)  Close cross odor nectar color irregular... 

monoacious dioecious.. .polygamous protandrous. 

protogynous heterostylous 

(2)  Means:  wind insects contact gravity water.. 

4.  Distinctive  recognition  characters 


f>.  Commercial  importance 


THE  SPRING  FLORA 


157 


Stem  section 


FIG.  26.    Vegetative  and  reproductive  parts  of  a  poplar 
Designed  to  indicate  the  method  of  recording  observations  on  trees 


1.  Twig,  buds 

Lenticels  and  scars 
Stem  section 


FIGURES 


2.  Leaf  characters 


3.  Inflorescence,  flower 

Long  section  of  flower,  pollination 


4.  Fruit  and  seed 

Fruit  class 

Seed  distribution. 


158         LABORATORY  AND  FIELD  EXERCISES 

FAMILY  RECORD 

Fill  in  the  analysis  and  the  distinctive  characteristics  of  each  species 
of  any  given  family  under  I  and  II. 

Fill  in  the  family  characteristics  common  to  all  species  observed 
under  III. 

Use  habitat,  habit,  and  reproduction  as  the  basis  for  your  characteri- 
zation of  the  family. 

I.  ANALYSIS 

Family . 

Scientific  name 

Common  name 

II.  DISTINCTIVK  CHARACTERISTICS 

IIabitat._. 


Habit. 


Reproduction.. 


II F.  FAMILY  CHAI 


[ACTKKISTICS 


THE  SPKING  FLORA  159 

GYMNOSPERMS  (SOFTWOOD  TREES) 

THE  PINE 

1.  Habitat. 

a.  What  is  the  nature  of  the  habitat  of  the  pines  of  your 

region  as  regards  soil,  drainage,  and  climate  ?  Do 
pines  grow  best  on  lowlands  or  on  well-drained 
slopes  and  uplands?  What  is  the  distribution  of 
pines  in  the  United  States  ?  What  is  their  natural 
habitat  as  regards  soil  and  climate  ?  Are  they 
mesophytic  or  xerophytic  in  general  habit  ?  How 
do  you  explain  the  apparent  discrepancy  between 
habitat  and  habit  in  the  pines  ?  Consult  the  text, 
manuals,  and  assigned  readings  on  the  above  points. 

b.  Summarize  the  above  points  in  your  notes  under  the 

following  headings: 

(1)  Habitat :  local geographical 

(2)  Habit :  mesophytic xerophytic 

(3)  Discrepancy  between  habitat  and  habit 

2.  Habit. 

a.  Form  and  body  plan  of  the  pine  tree. 

Eeview  the  text  discussion  of  the  body  plan  and 
mode  of  growth  of  the  pine  tree  in  Part  I  of  the  text. 
Consult  also  Fig.  10.  Be  able  to  account  for  the 
erect  conical  form,  the  excurrent  trunk,  and  the 
false  whorls  of  branches  of  common  pines.  Why 
is  the  trunk  excurrent  ?  What  determines  the  cone- 
like  form  of  the  entire  tree?  How  do  the  false 
whorls  arise  ?  Is  the  entire  leafage  well  exposed  to 
light  ?  What  factors  determine  this  light  exposure  ? 
Is  it  due  to  the  form  of  the  tree,  to  tropisms  of 
leaves  and  branches,  or  to  other  factors  ? 


160         LABORATORY  AND  FIELD  EXERCISES 

b.  Summarize  the  above  points  under  body  plan,  growth 

methods  of  buds  and  branches,  and  tropistic  responses 
of  leaves  and  branches. 

c.  Long  and  dwarf  shoots. 

Long  shoots  in  pines  are  the  main  branches  and 
twigs;  dwarf  shoots  are  the  small  structures  from 
which  the  needle  leaves  arise  in  clusters  of  two, 
three,  or  five. 

(1)  Study  long  and  dwarf  shoots  of  pines  in  the  field. 

Do  the  dwarf  shoots  arise  in  a  spiral  or  cyclic 
manner  from  the  long  shoots  ?  Study  the  naked 
portions  of  a  twig  where  the  scars  of  dwarf 
shoots  show  their  former  arrangement.  Observe 
the  scalelike  leaves  on  long  shoots.  What  is 
the  arrangement  of  the  scale  leaves  on  the  long 
and  dwarf  shoots  ?  Do  dwarf  shoots  arise  from 
the  axils  of  scale  leaves  like  ordinary  branches  ? 

(2)  Buds  and  growth.    Determine  the  nature  and  posi- 

tion of  buds  on  long  shoots.  Are  there  lateral 
buds  ?  Do  dwarf  shoots  arise  from  lateral  buds  ? 
Determine  the  age  of  a  terminal  portion  of  a  long 
shoot  by  the  rings  of  bud-scale  scars. 

(3)  Draw  a  small  portion  of  a  long  shoot  from  which 

dwarf  shoots  have  fallen,  to  show  their  arrange- 
ment on  the  long  shoot  and  their  relation  to  the 
scale  leaves.  Draw  the  terminal  portion  of  a  long 
shoot  to  show  the  shape  and  character  of  buds, 
dwarf  shoots,  and  needle  leaves.  It  is  best  not 
to  draw  more  than  one  or  two  dwarf  shoots  on 
the  terminal  shoot. 

d.  Strobili,  or  cones  (see  Fig.  233,  p.  379,  of  text). 

(1)  Ovuliferous  strobili.    Observe  the  position   of  the 
reproductive  cones  on  single  long  shoots  and  on 


THE  SPPvIXG  FLORA  161 

the  tree  as  a  whole.  Is  their  general  distribution 
and  their  individual  attitude  (due  to  tropistic 
response)  such  as  to  facilitate  the  distribution  of 
seeds?  Search  for  the  seeds.  What  adaptation 
have  they  for  dissemination  ?  What  is  the  plan 
of  arrangement  of  the  cone  scales  on  the  cone 
axis  ?  Does  it  correspond  to  the  body  plan  of 
the  tree? 

(2)  Young  strobili.  Do  you  find  strobili  of  different  ages 

on  the  pine  ?  Note  the  position  of  young  strobili 
How  long  does  it  take  pine  cones  to  mature  ? 

(3)  Staminate  and  ovulate  strobili    Do  you  find  both 

staminate  and  ovulate  strobili  on  the  same  tree? 
The  staminate  cones  can  only  be  found  in  late 
spring,  since  pollination  occurs  in  pines  about 
the  first  of  June. 

(4)  Make  simple   sketches   to  illustrate   the  positions 

on  the  branches  and  the  attitudes  assumed  by 
strobili  of  different  ages  and  kinds. 


ANGIOSPERMS  (HARDWOOD  TREES) 

FIELD  STUDIES 
1.  Habitat. 

a.  Local  habitat.    Study  the  conditions  under  which  the 

species  grows  in  the  local  habitat,  including  the  soil, 

water  supply,  and  drainage  conditions.    Which  one 

of  the  following  habitats  does  it  occupy  ? 

(1)  MesopJiytic  habitats.    Does  it  live  in  typical  upland 

mesophytic  conditions  or  is  it  found  on  lowlands 

such  as  flood  plains,  river  banks,  and  the  borders 

of  lakes  and  ponds  ?    Note  that  ornamental  trees 

are  frequently  not  growing  in  their  natural  habitat. 


L.VBOKATOEY  AND  FIELD  EXEK<  ISES 

(2)  Xerophytic  habitats.    Does  it  occupy  exposed  dry 

cliffs  and  hillsides,  sandy  regions,  or  mountain 
sides  without  adequate  water  supply  ?  Is  it 
found  in  marshes  or  swamps  which  are  physio- 
logically dry  on  account  of  the  condition  <>f  the 
bog  water  ? 

(3)  Hydrophytic  habitat.    Does  the  species  live  in  soil 

flooded  or  saturated  with  water  ? 

b.  Geographical  habitat  and  <K*tnb*tion.  Determine  the 
natural  habitat  and  distribution  of  the  species  on 
the  American  continent  by  means  of  manuals  and 
maps.  Consult  maps  and  descriptions  in  Hough's 
"  Handbook  of  North  American  Trees  "  if  this  work 
is  available.  Consult  the  text,  Fig.  223,  and  the 
discussion  of  trees  and  shrubs. 
2.  Habit. 

a.  Is  the  species  being  studied   mesophytic,  xerophytic, 

hydrophytic,  or  tropophytic  in  habit  ? 

b.  Size  and  form.    Is  it  large  or  small  as  compared  with 

other  trees  in  the  region  ?  Is  it  erect  or  spreading  in 
habit  ?  Is  there  a  single  excurreut  trunk  or  does  the 
trunk  divide  above  into  two  or  more  secondary  axes  ? 

c.  Body  plan  and  development.    Review  the  text  discus- 

sion in  Part  I  on  the  development  of  trees  and  its 
relation  to  body  plan,  bud  growth,  and  pruning  in 
the  spruce  and  elm.  See  Fig.  11  of  text. 

d.  Study  the  relation  of  the  following  four  main  factors, 

which  determine  the  form  of  a  tree,  to  the  ultimate 
form  assumed  by  the  species  you  are  observing,  as 
indicated  below: 

(1)  Body  plan.  Is  the  species  you  are  studying  cyclic 
or  spiral  in  leaf  and  bud  arrangement  ?  If  spiral, 
is  the  phyllotaxy  J,  f ,  f ,  or  a  higher  fraction  ? 


THE  SPUING  FLOEA  103 

(2)  Buds  and  growth.    Is  there  a  main  terminal  bud, 

as  in  the  pine,  producing  a  single  excurrent 
trunk,  or  is  the  main  terminal  bud  superseded 
by  one  or  more  laterals  which  produce  a  sub- 
division of  the  trunk  above  ?  How  many  lateral 
buds  produce  strong  shoots  each  season?  Consult 
the  growths  of  the  last  four  or  five  years  on  the 
terminal  portions  of  branches.  How  many  buds 
remain  latent  or  produce  weak  lateral  twigs 
each  season  ? 

(3)  Pruning  •#'•••*#.    Determine  the  effect  of  natural 

and  artificial  pruning  on  the  form  of  the  tree. 
Do  small  unsuccessful  twigs  or  shoots  continue 
to  form  a  part  of  the  crown  of  the  tree  or  is 
the  crown  composed  wholly  of  the  more  vigorous 
shoots  of  past  seasons  ? 

(4)  Adju*tmt'ntx  t"  tie-  i-nrir»nment  by  tropisms.   Observe 

the  position  of  branches  in  the  upper,  middle,  and 

lower  thirds  of  the  crown.    Is  the  form  of  the 

branches   and   their  position  "with   reference  to 

the  main  or  to  the  secondary  axes  different  in 

the  above  portions  of  the  crown  ?   Is  the  response 

mainly  to  light  or  to  gravity  ?   Do  the  positions 

assumed  by  the  branches  secure  a  better  light 

exposure  for  the  leaves  and  a  better  position  for 

the  dissemination  of  fruits  and  seeds  ? 

e.  Baric.  Compare  the  bark  on  the  main  trunk  and  its 

branches.    Is  there  a  marked  difference  in  color,  and 

in  smoothness  or  roughness,  between  the  bark  on 

the    branches    of    the    upper    and    middle   portions 

of  the  crown  and  that  of  the  main  trunk  and  its 

larger   subdivisions  -?     Is  the  difference  such  as  to 

form  a  distinctive  characteristic  of  the  species  under 


CANOtf    BIRCH  BEECH 

Chalky  white  horizontal  lines          Smooth,  qr&y,  mettled 

n 


CHESTNUT  WHITE    OAK 

Long  eorvfluent  ridges  Long  narrow  yiat  scales 


UMBRELLA    TREE 
Smooth,  blister  like 


SASSAFRAS 
Rough  broken  ridges 


Three  kinds  of  bark  —  smooth,  ridged,  and  scaly.    (After  Mathews) 


THE  SPRING  FLOKA  165 

examination  ?  Is  the  bark  on  the  trunk  rough  or 
smooth,  furrowed  or  flaky,  corky  or  indurated,  in 
texture  ? 

f.  Leaves  and   the  liyht  relation.  Observe  the   form  and 

texture  of  the  leaves  and  their  arrangement  with 
reference  to  light.  Have  they  distinct  differences  in 
form  and  arrangement  which  facilitate  lighting  by 
the  sun  ?  Have  they  distinct  organs  or  methods  for 
tropistic  response  which  expose  them  favorably  to 
light  ?  Do  they  form  mosaics  ? 

g.  Outline  sketch.  Draw  an  outline  sketch,  similar  to  the 

figures  of  the  elm  in  Part  I,  to  illustrate  the  above 
points  relative  to  habit.  For  the  first  studies  the 
student  may  well  draw  a  series  of  figures,  similar  to 
Fig.  11,  a-f,  to  show  the  relation  of  body  plan,  growth, 
and  pruning  to  the  ultimate  form  and  leaf  exposure 
of  the  tree. 

3.  Reproduction.    Study  the  inflorescence,  flowers,  fruits,  and 
seeds  of  the  species  you  are  observing,  as  follows : 

a.  Inflorescence.  Are  the  flowers  solitary  in  the  axils  of 

leaves  or  are  they  borne  in  clusters  ?  In  the  latter 
case  determine  the  kind  and  the  general  structure 
of  the  inflorescence.  Consult  the  text  description 
of  the  kinds  of  inflorescence  under  Descriptive  Terms. 

b.  Floivers.  Study  the  structure,  floral  plan,  and  pollina- 

tion features  of  the  flowers  under  the  following 
headings,  determining  which  terms  are  applicable  to 
the  species  being  studied.  Consult  the  text  under 
Descriptive  Terms. 

(1)  Structure.  Are  the  flowers  complete  or  incomplete, 
perfect  or  imperfect,  regular  or  irregular  in  form  ? 
Are  they  hypogynous,  perigynous,  or  epigynous 
in  the  relation  of  their  floral  parts  ? 


166         LABORATORY  AND  FIELD  EXERCISES 

(2)  Floral  plan.  Are  the  flowers  spiral  or  cyclic  in  the 

arrangement  of  their  parts  on  the  receptacle? 
Are  they  on  the  plan  of  3,  4,  or  5  ? 

(3)  Pollination  features.   Study  the  adaptations,  if  any, 

which  the  flowers  possess  for  securing  pollination, 
as  well  as  the  means  or  agents  by  which  pollina- 
tion is  secured.  Be  able  to  designate  those  of  the 
following  terms  which  apply  to  the  flowers  under 
observation.  Are  they  close-pollinating,  cross- 
pollinating,  or  self-pollinating  ?  Have  they  color, 
odor,  nectar,  or  any  other  attractive  features  for 
securing  insect  pollination  ;  that  is,  are  they  ento- 
mophilous  ?  Are  they  adapted  for  wind  pollina- 
tion ;  that  is,  are  they  anemophilous  ?  If  so,  be 
able  to  state  the  adaptation. 

c.  Fruit  and  seed.    Study  the  nature  of  the  fruit  and  its 

origin  from  the  pistil.  Are  there  special  devices  for 
seed  and  fruit  dissemination  ?  Do  you  know  of  any 
wild  tract  which  has  been  seeded  by  fruits  dissemi- 
nated from  near  or  distant  trees  of  the  species  you 
are  studying  ?  In  what  places  in  your  region  are 
trees  most  successful  in  producing  offspring  by  seed 
dissemination  ?  In  what  places  in  other  regions  ? 
Considering  the  large  number  of  seeds  produced  by 
each  tree,  why  are  trees  not  more  abundant  ? 

d.  Drawings.  Make  sketches  to  illustrate  the  structure, 

floral  plan,  and  pollination  features  of  the  flower.  Draw 
the  fruits  and  label  all  parts  correctly.  These  draw- 
ings can  be  made  separately  or  with  other  drawings 
of  the  species,  as  in  the  poplar,  on  the  Species  Record. 
4.  Anatomy.  Cut  gross  transverse  sections  of  twigs  or  small 

branches.    Observe   the  nature   of  the  wood,  phloem, 

and  bark. 


THE  SPRING  FLORA  167 

a.  Is  the  wood  porous  or  dense  ?  ring  porous  (with  pores 

in  the  spring  wood)  or  diffuse  porous  (with  pores  in 
both  spring  and  summer  wood)  ?  Is  the  wood  hard  or 
soft  ?  Do  you  think  it  would  be  commercially  valua- 
ble ?  Draw.  See  drawings  of  the  poplar  for  a  model. 

b.  Commercial  importance.    Find  out  if  possible  the  com- 

mercial importance  of  the  wood  in  the  species  being 
studied.  See  figures  and  discussions  in  the  text  on 
the  above  points. 

5.  Distinctive  recognition  characters.  What  distinctive  char- 

acters would  enable  you  to  recognize  the  tree  you  are 
studying  in  the  field  ?  Are  there  distinctive  characters 
of  the  species  other  than  gross  external  ones  ?  Summarize 
the  distinctive  characters  under  the  record  of  results. 

6.  Analysis.    Analyze  the  species,  to  determine  the  family 

to  which  it  belongs  and  the  scientific  and  common 
species  names.  Record  the  family,  genus,  and  species 
on  the  Species  Record. 

B.  HERBACEOUS  DICOTYLEDONS 
A  METHOD  OF  RECORDING  FIELD  OBSERVATIONS 

The  method  submitted  below  of  recording  field  observations 
for  herbaceous  plants  is  similar  to  that  indicated  for  trees 
and  shrubs.  The  plan  may  be  followed  for  a  part  of  the  field 
work  if  desired,  until  the  student  is  familiar  with  methods  of 
observing  and  recording  results.  It  should  not  be  carried  to 
the  point  of  becoming  mechanical.  After  the  first  detailed 
studies  have  been  recorded  on  the  Species  Record  form,  teachers 
may  prefer  to  use  the  Family  Record  exclusively.  Loose-leaf 
sheets  for  species  and  family  records  are  convenient  and  are 
used  by  the  author  in  field  work.  These  can  be  printed  by  a 
local  printer  from  the  outlines  in  these  exercises. 


168         LABORATORY  AND  FIELD  EXERCISES 

SPECIES  RECOKD 
I.  ANALYSIS 

Family 

Scientific  name 

Common  name Locality 

II.  CHARACTERISTICS  :  monocotyledon dicotyledon 

1.  Habitat:  mesophytic xerophytic hydrophytic 

2.  Habit:  mesophyte jxerophyte hydrophyte 

a.  Stem  :  caulescent... branching... height. acaulescent___ 

erect horizontal prostrate climbing rhizome 

bulb.._corm___tuber__. 
Tropisms  :   pro dia apo 

b.  Leaves:  large small medium__^__simple compound 

(1)  Venation  :  netted parallel pinnate palmate 

(2)  Position  :  radicaL__cauline_._spiral.._cyclic.— decussate 

(3)  Orientation  :  horizontal vertical oblique rosette____ 

mosaics 

(4)  Light  tropisms:    pro dia apo 

c.  Roots:  primary __. lateral ___fibrous...fleshy___  surface___deep.__. 

Gravity  tropisms  :  pro dia apo 

3.  Reproduction 

a.  Inflorescence :  solitary determinate indeterminate 

kind..  

It.  Flower  characters:  hypogynous perigyiious epigynous 

perfect imperfect regular irregular 

c.  Pollination  features 

(1)  Cross  :  odor.____nectar____color____irregular____unisexual 

(2)  Close:  odor nectar color regular bisexual 

(3)  Special  features:  protandry...protogyny.___heterostyly._. 

(4)  Means  :  wind insects contact gravity water. 

4.  Distinctive  characters 


THE  SPRING  FLORA  169 


FIGURES 

1.  Stem,  root,  leaf  •>•  Inflorescence  and  flower 

Ihihit  and  tropisms  Long  sections  and  ground  plan 

Pollination  features 


Detail :  anther  dehiscence, 
carpels,  placenta;,  ovules 


2    Stem  section 

Epidermis,  cortex,  vascular 
cylinder,  stem,  pith 


4.  Fruit  and  seed 

Fruit  class 

Seed  dispersal 


170         LABORATORY  AND  FIELD  EXERCISES 

FAMILY  RECORD 

Fill  in  the  analysis  and  the  distinctive  characteristics  of  each  species 
of  any  given  family  under  I  and  II. 

Fill  in  the  family  characteristics  common  to  all  species  observed 
under  III. 

Use  habitat,  habit,  and  reproduction  as  the  basis  for  your  characteri- 
zation of  the  family. 

I.  ANALYSIS 

Family 

Scientific  name 

Common  name 


II.  DISTINCTIVE  CHARACTERISTICS 

• 
Habitat.... 


Habit.. 


Reproduction. 


III.  FAMILY  CHARACTERISTICS. 


THE  SPKING  FLOKA  171 

RANUNCULACEAE  (BUTTERCUP  FAMILY) 
BUTTERCUP  OR  HEPATICA 

Select  one  or  more  species  of  buttercups  for  field  study. 

1.  Habitat.    Determine  the  following  facts  concerning  the 

habitat  of  buttercups : 

a.  Soil,  water  supply,  and  drainage  of  their  habitat  at 
different  seasons  of  the  year. 

&.  Plant  associates.  With  what  other  plants  are  the 
buttercups  associated  ?  Does  their  association  with 
these  plants  affect  their  relation  to  light,  soil  mois- 
ture, and  soil  food  ?  Would  these  relations  be  different 
at  different  seasons  of  the  year  ?  Be  able  to  explain 
the  relation  of  this  association  to  the  spring  flower- 
ing period  of  buttercups  or  hepaticas.  * 

2.  Habit.    Use  Ranunculus  fascicularis  for  this  study  if  it 

is  available.  Other  species  may  be  used.  Study  plants 
of  Ranunculus  fascicularis  in  the  field ;  remove  some 
plants  from  the  soil  with  a  trowel  so  as  not  to  injure  the 
root  system,  and  observe  as  follows : 

a.  Stem,  roots,  and  leaves.    Note  the  origin  of  the  roots 

and  leaves  from  the  short  (acaulescent)  stem.  Are 
the  leaves  cyclic  or  spiral  in  arrangement  ? 

b.  Light  relation.     What  position  do  the  leaves  assume 

with  reference  to  light?  Are  they  advantageously 
placed  ?  Is  this  favorable  placing  of  the  leaves  a  re- 
sultant of  both  body  plan  and  adjustment  by  tropisms, 
as  in  peas,  dandelions,  and  trees  studied  earlier  in  the 
text  ?  Be  able  to  explain. 

c.  Soil  relation.     Study  the  root  system  of  Ranunculus 

fascicularis.  What  different  kinds  of  roots  do  you 
find  ?  What  is  the  apparent  function  of  each  ?  At 


172         LABORATORY  AND  FIELD  EXERCISES 

what  season  do  the  different  kinds  of  roots  originate? 
Note  the  place  of  origin  of  each  kind  of  root  from 
the  stem  in  young  and  mature  plants.  Do  they 
originate  at  the  same  time  and  in  the  same  manner? 
Save  your  specimen  for  a  drawing  in  connection 
with  the  seasonal  life  of  the  buttercup. 
d.  Summarize  the  above  facts  relating  to  habitat  and 
habit  in  your  notes  or  on  a  Field  Species  Record. 

3.  Reproduction. 

a.  Flower    scapes.    Note    the    origin,   and    the    position 

assumed  by  the  flower  scapes.  What  outside  forces 
act  as  stimuli  in  orienting  the  flower  scapes  ?  Are 
they  adjusted  so  as  to  expose  the  flowers  and  fruits 
properly  for  pollination  and  seed  dissemination  ? 

b.  Flowers.    What  is  the  floral  plan  of  the  flowers  luider 
*  observation  ?  What  are  the  adaptations  for  pollination  ? 

Is  the  flower  self-pollinating,  close-pollinating,  or 
cross-pollinating?  Note  any  special  devices  for 
pollination. 

c.  Eecord  your  observations  in  the  Species  Eecord  under 

Pollination  features.  Construct  suitable  drawings  to 
show  the  pollinating  device. 

d.  Fruit  and  seeds.    To  what  class  of  fruits  do  the  fruits 

of  the  plants  you  are  observing  belong  ?  Consult 
the  text,  under  Descriptive  Terms  in  Part  III,  and 
Fig.  221.  Eecord  your  results  by  drawings  and  terms 
giving  the  kind  and  class  of  the  fruit. 

4.  Seasonal  life.    Are  the  buttercups  and  hepaticas  annual, 

biennial,  or  perennial  plants  ?  What  advantage  is  it  to 
them  that  they  flower  in  spring  ?  Consider  this  point 
in  connection  with  their  plant  associates  and  their 
habitat.  Is  their  active  food-building,  like  their  repro- 
ductive functions,  carried  on  mainly  in  the  spring? 


THE  SPRING  FLORA  173 

What  is  the  function  of  the  fleshy  roots  of  Ranunculus 
fasdcularis  in  its  seasonal  history  ?  Construct  figures 
corresponding  to  those  of  the  white  sweet  clover 
(Fig.  65)  and  the  dandelion  (Fig.  24)  in  Part  I  of  the 
text,  to  express  the  habit  and  the  seasonal  life  of 
Ranunculus  fascicularis  or  the  other  species  observed. 
Summarize  these  facts  in  your  notes  or  in  the  Species 
Record. 
5.  Analysis.  Analyze  one  or  more  species  of  Ranunculaceae. 

FLORAL  MODIFICATIONS  IN  RAxrx<TLACEAE: 
COLUMBINE  (AQUILEGIA) 

1.  Compare  the  columbine  (AquUegid)  with  typical  Ranun- 

culaceae as  regards  habitat,  habit,  and  reproduction, 
noting  the  variations  in  the  columbine  from  buttercups 
and  the  marsh  marigold. 

2.  Reproduction. 

a.  Pollination.  What  floral  arrangements  facilitate  polli- 
nation ?  Are  the  flowers  protandrous  or  protogy nous  ? 
Is  self-pollination  possible?  Make  a  sketch  to  illus- 
trate the  method  of  pollination  in  Aquilegia  and 
compare  it  with  Fig.  250.  Summarize  the  devices 
for  securing  cross-pollination  which  obtain  in  the 
columbine. 

l>.  Fruit  and  seed.  Compare  with  that  of  the  buttercup. 
What  is  the  method  of  shedding  and  disseminating 
seed  ? 

VIOLACEAE 

1.  Habitat  and  habit.    Study  the  habitat  and  habit  of  the 

Violaceae   in   the   same   manner   as   that  outlined   for 

the  buttercup.   What  are  their  plant  associates  ?  Would 

•     violets  have  as  good  an  opportunity  for  flowering  and 


174         LABORATORY  AND  FIELD  EXERCISES 

setting  seed  in  the  summer  and  autumn  as  in   the 
spring?    Be  able  to  explain  this  point. 

2.  Seasonal  life. 

a.  Compare  the  seasonal  life  of  violets  and  buttercups. 

What  are  the  principal  activities  of  the  violet  plant 
in  spring,  autumn,  summer,  and  winter  ?  What  por- 
tions of  the  plant  are  active  at  each  season?  Consult 
the  text,  Part  I,  on  seasonal  life. 

b.  Summarize  the  above  facts  relating  to   the  seasonal 

history  of  violets. 

3.  Reproduction.    The  flower  and  its  modifications  for  secur- 

ing pollination. 

a.  Study  the  parts  of  the  flower  and  their  modifications. 

What  modifications  do  you  find  in  the  perianth  and 
the  essential  organs  ?  Remove  the  parts  of  the  peri- 
anth and  observe  their  form  and  structure.  Note 
the  relation  of  the  stamens  to  the  perianth  and 
to  the  pistil. 

b.  Cut  a  transverse  section  across  a  flower  in  the  region  of 

the  ovary.  Study  the  section  and  construct  a  ground 
plan  of  the  violet  flower  which  will  show  the  relation 
of  the  parts  of  the  perianth  and  the  essential  organs. 

c.  Pistil  and  stamens. 

(1)  Dissect  away  all  of  the  petals  except  the  lower  one 

with  the  spurlike  nectary.  Examine  the  stigma 
and  anthers  with  a  hand  lens.  Where  is  the  stig- 
matic  surface  ?  How  is  it  related  to  the  anthers 
and  to  the  canal  leading  to  the  nectary  ?  Where 
is  the  pollen  shed  ? 

(2)  Bisect  a  flower  longitudinally  and  study  the  above 

relation  of  pistil,  stigma,  and  anthers  to  the  nec- 
tary and  the  lower  petal.  Consult  Fig.  253  of 
text  and  the  discussion  on  pollination. 


THE  SPKING  FLOBA  175 

d.  Pollination.    How  is  pollination  secured  through  the 

agency  of  visiting  insects  ? 

e.  Drawing.    Draw  a  median  long  section  of  the  flower 

to  show  the  relation  of  the  floral  parts  which  insure 
cross-pollination.  Label  accurately. 

f.  Summarize  under  the  following  headings  the  mechanisms 
of  the  violet  which  adapt  it  for  cross-pollination. 

(1)  Perianth  modifications. 

(2)  The  relation  of  the  pistil,  stigma,  and  anthers. 

(3)  The  anther  tube  and  pollen  shedding. 

(4)  The  relation  of  a  visiting  insect  to  the  flower  in 

securing  nectar. 

4.  Analysis.    Analyze  one  or  more  species  of  violets,  record- 
ing the  family,  scientific,  and  common  name. 

CRUCIFERAE 

Study   the   habitat   and   habit   of   some   of    the   important 
members  of  the  cruciferous  family. 

1.  Habit. 

a.  Stem  and  roots.    What  are  the  distinctive  features  of  the 

stems  and  roots  of  the  Cruciferae  that  you  are  study- 
ing ?  Are  there  characteristics  which  are  unusual  ? 
What  is  the  nature  of  the  juice  or  sap  ? 

b.  Leaves.   Observe  any  distinctive  characteristics  of  leaves 

in  members  of  the  family  under  observation. 

2.  Reproduction. 

a.  Determine   the   nature   of   the   inflorescence   and   the 

structure  of  the  flower. 

b.  Drawings.  Draw  a  ground  plan  of  a  flower  of  some  one 

of  the  Cruciferae.  Draw  a  median  long  section  of  a 
flower  to  show  the  relation  of  the  perianth,  stamens, 
and  pistil. 


176         LABORATORY  AND  FIELD  EXERCISES 

c.  Pollination. 

1.  What  are  the  special  devices  for  securing  pollina- 

tion ?  To  determine  this  point  study  flowers  of 
different  ages  and  note  the  relation  of  the  differ- 
ent lengths  of  stamens  to  the  stigmatic  surface. 
Does  this  relation  change  as  the  flower  matures  ? 

2.  Construct  outline  drawings  to  illustrate  any  devices 

for  self-pollination,  close-pollination,  or  cross- 
pollination  which  you  discover. 

d.  Fruit  and  seed.   Study  and  classify  fruits  011  one  or 

more  species  of  the  Qruciferae.  Construct  a  diagram 
of  the  fruit  to  show  its  method  of  dehiscence. 

3.  Seasonal  life.  Study  the  seasonal  life  of  some  of  the  more 

important  cultivated  species  of  the  Cruciferae  in  the 
field  and  by  consulting  text  references.  See,  for  example, 
Bailey's  "Encyclopedia  of  Horticulture,"  Robbins's 
"  Botany  of  Crop  Plants,"  and  Sargent's  "  Plants  and 
their  Uses." 

a.  Are  the  members  of  the  family  mainly  annuals,  bien- 

nials, or  perennials  ?  How  do  the  biennials  and  peren- 
nials pass  the  winter  ? 

b.  Construct  a  series  of  diagrams  to  illustrate  the  seasonal 

life  of  one  important  commercial  variety  of  the  Cru- 
ciferae.  Consult  the  text,  Part  I,  on  the  seasonal  life 
of  the  bean,  clover,  and  locust. 

4.  Commercial  importance.  Make  a  list  of  the  more  important 

species  of  Cruciferae  and  indicate  the  use  of  each  species. 

5.  Analysis.    Analyze  species  of  the  Cruciferae^  recording 

the  family,  species,  and  common  name. 

6.  Distinctive  characteristics.   Summarize  under  habit,  repro- 

duction, and  seasonal  life.  The  above  data  may  be 
recorded  on  a  Species  Eecord  or  a  Family  Eecord  sheet 
if  desired. 


THE  SPRING  FLORA  177 

LEGUMINOSAE 

See  Pollination  devices  in  papilionaceous  flowers  in  Part  I 
of  the  text,  and  the  seasonal  history  of  the  bean  and  the  white 
sweet  clover.  See  also  previous  laboratory  work  and  drawings 
011  the  locust  and  sweet  pea.  Study  the  distinctive  recognition 
characters  of  representative  species  of  Leguminosae  in  the  field 
and  be  able  to  summarize  them  under  the  following  headings : 

1.  Habit. 

a.  Stems.  Are  the  stems  all  herbaceous  in  character  or 
are  there  some  common  trees  and  shrubs  belonging 
to  the  family  ? 

./>.  Leaves.  What  are  the  distinctive  structural  and  physio- 
logical features  of  the  leaves  of  all  Leguminosae 
which  distinguish  them  from  other  families  of  plants 
with  which  you  are  familiar  ?  Study  the  leaves  of 
several  species  and  their  reactions  to  light.  Are 
they  simple  or  compound  ?  Have  they  special  motor 
organs  ? 

c.  Roots.  Dig  up  the  root  system  of  the  common  red 
clover,  of  the  pea,  or  of  the  bean.  Do  you  find  en- 
largements on  various  parts  of  the  root  system  in  the 
form  of  nodules?  These  nodules  contain  the  nitrogen- 
gathering  bacteria  which  enable  these  plants  to  use 
free  nitrogen  from  the  soil.  Observe  also  the  extent 
of  the  root  system  as  compared  with  the  leaf  system. 
Is  the  root  surface  exposed  to  the  air  ? 

2.  Reproduction. 
a.  Flowers. 

(1)  Structure.  Have  the'flowers  of  the  family  a  common 
structure,  floral  plan,  and  form  ?  Note  any  floral 
modifications  from  the  usual  type  of  the  flowers 
of  the  family  illustrated  in  the  text. 


178         LABORATORY  AND  FIELD  EXERCISES 

(2)  Pollination.  Are  all  of  the  flowers  of  the  family 
cross-pollinated  ?  Compare  the  methods  of  pollina- 
tion in  peas,  clovers,  and  vetches. 

b.  Fruits  and  seeds.  Do  you  find  all  fruits  in  the  family 

similar  to  that  of  the  pea,  bean,  and  locust  ? 

c.  Summary.  Summarize  the  distinctive  characteristics  of 

the  Leguminosae  under  the  above  headings  and  in 
the  order  indicated  in  the  directions.    This  may  be 
done  on  a  Family  Record  sheet  if  desired. 
3.  Economic  importance.  Study  species  which  are  of  economic 
and  commercial  importance  in  the  family  as  indicated 
under  the  Cruciferae.    List  several  important  commer- 
cial species  and  the  particular  uses  of  each  species. 

SUPPLEMENTAKY  STUDY 

Each  student  should  be  assigned  some  species  of  the  Leyuminosae, 
such  as  the  common  red  clover,  vetch,  or  lupine,  for  individual 
study  and  report.  The  report  should  include  drawings  to  show 
the  following  structures : 

1.  Habit. 

a.  Leaves.  Observe  the  mechanism  for  adjustments  of  leaves 

to  light,  including  the  position  of  leaves  in  the  morn- 
ing, at  noon,  and  at  night.  Make  a  brief  statement  of 
the  mechanism  of  movement  in  leaves  with  pulvini. 

b.  Roots.  Drawings  of  roots  with  tubercles. 

c.  Reproduction.  Observe   and  record   the   following   facts 

relating  to  the  flowers,  fruits,  and  pollination : 

(1)  The  structure  of  the  flower  and  pollinating  mechanisms. 

(2)  Fruit  and  methods  of  seed  dispersal. 

(3)  A  brief  discussion  of  the  pollinating  mechanism  and 

of  seed  dispersal  in  such  a  species  as  the  common 
red  clover. 

d.  Analysis.  Analyze  two  or  more  species  of 

and  record  as  usual. 


THE  SPRING  FLORA  179 

ROSACEAE 
STRAWBERRY  (FRAG ARIA]  OR  POTENTILLA  (CINQUEFOIL) 

1.  Habit. 

a.  Observe  the  general  habit  of  the  strawberry,  noting 
the  relations  of  stem,  leaves,  and  roots. 

2.  Reproduction. 

a.  Vegetative  reproduction.  Study  the  origin  of  the  run- 
ners, and  their  general  morphology.  Do  they  origi- 
nate, like  stems,  from  the  axils  of  the  leaves?  Have 
they  nodes,  internodes,  and  leaves?  How  do  the 
runners  produce  offspring  ? 

b.  Construct  a  diagram  to  illustrate  the  origin,  morphol- 

ogy, and  mode  of  reproduction  by  runners. 

c.  The  flower.     Study  the   floral   plan   and   structure  of 

the  flower.  Be  able  to  construct  a  ground  plan  of 
a  flower. 

d.  Pollination  features.    Read  the  text  on  Fragaria  and 

consult  the  figures.  Determine  the  method  of  polli- 
nation in  the  species  or  variety  that  you  are  study- 
ing. Construct  figures  to  illustrate  the  method  of 
pollination  observed. 

e.  Flower  and  fruit. 

(1)  To  what  class  of  fruits  does  the  strawberry  belong  ? 

What  are  its  parts  and  how  are  they  related  to 
the  similar  parts  of  the  flower  ?  Bisect  a  fruit 
lengthwise  and  compare  it  with  a  similar  section 
of  the  flower.  Be  able  to  name  corresponding 
parts  in  the  flower  and  the  fruit. 

(2)  Drawings.    Draw  a  median  vertical  section  of  the 

flower  and  fruit  of  the  strawberry  and  name 
the  corresponding  parts. 


180         LABORATORY  AND  FIELD  EXERCISES 

THE  CULTIVATED  APPLE  (MALUS) 

1.  Habit. 

a.  Form  and  body  plan.    Be  able  to  account  for  the  form 

and  leaf  display  of  the  apple  tree,  as  for  the  elm 
and  pine  in  Part  I  of  the  text.  Determine  this  on 
the  hasis  of  body  plan,  bud  growth,  pruning  effects, 
and  adjustments  of  leaves  and  branches  by  tropisms. 

b.  Suds  and  fruit  spurs. 

(1)  Where  are  the  fruit-bearing  branches  (fruit  spurs) 

located  on«the  main  branches  of  the  tree  ?  Search 
for  bud-scale  scars,  and  leaf  and  fruit  scars  on 
the  short  fruit  spurs  or  spur  shoots.  The  fruit 
scar  is  usually  a  large,  circular  scar  surrounded 
by  smaller  scars  representing  the  scars  of  un- 
developed fruits  in  the  same  flower  cluster.  How 
many  years  old  are  the  spur  shoots  that  you 
are  examining? 

(2)  Draw  a  terminal  shoot  of  an  apple  branch,  indicat- 

ing the  position,  form,  and  markings  of  the 
spur  shoots. 

2.  Reproduction. 

a.  Inflorescence.    To  what  class  of  inflorescence  does  that 

of  the  apple  belong  ? 

b.  Flower  structure.    Is  the  flower  epigynous,  perigyuous, 

or  hypogynous  ?  Determine  the  relations  of  recep- 
tacle, perianth,  stamens,  and  pistil. 

c.  Pollination.    Determine  the  method  of  pollination  in 

the  apple  flower.  Is  the  method  of  pollination  of 
economic  importance  ?  Be  able  to  explain  this  point. 

d.  Flower  and  fruit. 

(1)  Study  transverse  and  long  sections  of  the  fruit. 
What  parts  of  the  flower  are  represented  in  the 
fruit?  What  parts  are  lacking?  What  parts 


THE  SPRING  FLORA  181 

have  increased  in  size  and  what  parts  have 
become  otherwise  changed  ? 

(2)  Drawings.   Draw  a  transverse  and  a  vertical  median 

section  of  the  flower  of  the  apple,  magnified 
sufficiently  to  show  clearly  the  parts  of  the  ovary 
and  the  ovules. 

(3)  Discuss  briefly  the  parts  of  the  flower  which  enter 

into  the  formation  of  fruit,  and  the  changes 
undergone  during  fruit  formation. 

3.  Reference  readings.  Consult  various  texts  concerning  the 
history  and  reproduction  of  the  cultivated  strawberry 
and  apple.  Eobbins's  "  Botany  of  Crop  Plants "  is 
particularly  valuable  as  a  reference  on  the  above  points. 
See  also  Bailey's  ''American  Horticulture." 

SUPPLE  ME  NT  A  R  Y  STUDY 

1.  If  time  allows,  the  student  should  study  the  flowers  and 
fruits  of  the  wild  rose,  cherry,  raspberry,  and  blackberry,  in  order 
to   acquaint   himself  with  the   methods   of   fruit   formation  in 
these   important   fruit-bearing   species. 

2.  Commercial  varieties.  Study  and  record  important  commer- 
cial species  and  varieties  of  the  Rosaceae,  as  for  the  Cruciferae 
and  Leguminosae. 

COMPOSITAE 

THE  YARROW  (ACHILLEA) 

Read  the  text  discussion  of  the  inflorescence,  flowers,  and 
fruits  of  the  common  yarrow  and  confirm  the  points  there 
discussed. 

1.  Inflorescence.  To  what  class  of  inflorescence  does  that  of 
the  yarrow  belong  ?  Bisect  the  inflorescence  vertically 
and  study  its  parts.  What  is  the  form  of  the  axis  of 
inflorescence  ?  What  structures  make  up  the  involucre  ? 


182         LABORATORY  AND  FIELD  EXERCISES 

To  what  structures  do  these  parts  of  the  involucre  of 
the  yarrow  correspond  in  a  raceme  or  spike  ?  How  are 
the  flowers  of  the  inflorescence  differentiated  ?  Is  there 
any  conceivable  advantage  in  this  differentiation  ?  Does 
each  separate  flower  spring  from  a  separate  bract? 
Compare  the  parts  of  the  inflorescence  of  the  yarrow 
with  that  of  a  raceme. 

2.  Flowers. 

a.  Central  tubular  flowers. 

(1)  Study  these  flowers  with  a  hand  lens  and  deter- 

mine ttie  relation  of  calyx,  corolla,  stamens,  and 
pistil.  Is  there  anything  corresponding  to  a  calyx? 

(2)  Are  the  flowers  hypogynous,  perigynous,  or  epigy- 

nous  ?    Are  they  perfect  or  imperfect  ?  complete 
or  incomplete  ?  regular  or  irregular  ? 

(3)  Note  the  bract  subtending  each  flower. 

b.  Outer  ray  flowers.  What  is  the  function    of   the  ray 

flowers  ?  Compare  these  with  the  central  tubular 
flowers.  Are  the  essential  organs  present  ?  How  is 
the  corolla  modified  ? 

3.  Pollination.     Split   the    corolla   of    young   and    mature 

tubular  flowers  with  dissecting  needles  so  as  to 
expose  the  stamen  tube  and  style.  Compare  the 
young  and  old  flowers  as  follows  (consult  the  text 
figure) : 

a.  Note  a  stage  where  the  upper  portion  of  the  style 

is  still  within  the  anther  tube.  Where  are  the 
stigmatic  surfaces  ?  Is  the  pollen  being  shed  ?  Can 
it  reach  the  stigma  ? 

b.  Observe   a   slightly   older  stage.     Are   the   stigmatic 

surfaces  exposed  ?  Can  they  be  self-pollinated  ? 
Are  the  flowers  of  the  yarrow  protandrous  or 
protogynous  ? 


THE  SPRING  FLORA  183 

4.  Fruit  and  seed.    To  what  class  of  fruits  does  that  of  the 

yarrow  belong  ?  Is  there  any  definite  device  for  seed 
and  fruit  dispersal  ? 

5.  Summary.   Summarize   the   distinctive   features    of   the 

yarrow,  as  a  representative  of  the  Oompositae,  under 
the  above  headings ;  namely,  inflorescence,  flowers,  polli- 
nation, and  fruit.  Give  the  distinctive  features  only. 

6.  Analysis.    Ascertain  the  scientific  name  of  the  yarrow  by 

means  of  a  manual. 


DAXDELIOX  (TARAXACUM) 

1.  Habit  and  adjustments  by  tropisms. 

a.  Study  the  plants  of  the  dandelion  in  flower  and  deter- 
mine the  relations  of  its  organs  to  each  other  and  to 
the  environment.  Consult  the  text  discussion  (Part  I) 
concerning  the  adjustments  of  the  leaves,  flowers, 
and  fruits  for  photosynthesis,  food  absorption,  polli- 
nation, and  seed  dispersal.  Confirm  these  points  by 
field  observations. 

2.  Reproduction. 

a.  Vegetative  reproduction. 

(1)  Dig  up  a  number  of  plants  of  the  dandelion.  Is  the 

stem  simple  or  branched  ?  Do  you  discover  how 
a  single  plant  may  give  rise  to  a  group  of  offspring 
by  vegetative  reproduction  ? 

(2)  Construct  outline  figures  to  illustrate  what  you  find 

in  this  respect. 

b.  Inflorescence  and  flowers. 

(1)  Compare  the  general  structural  parts  of  the  inflores- 
cence and  flower  of  the  dandelion  with  that  of 
the  yarrow.  In  what  respects  are  they  similar  ? 
In  what  respects  do  they  differ  ? 


184         LABORATORY  AND  FIELD  EXERCISES 

(2)  Summarize  the  similarities  and  differences  of  the 

inflorescence  and  flowers  which  you  have  observed 
in  comparing  the  dandelion  with  the  yarrow. 

(3)  Pollination,    Proceed  as  directed  under  the  labora- 

tory directions  on  the  yarrow  to  find  out  the 
mechanism  of  pollination  in  the  dandelion.  Com- 
pare with  the  yarrow  in  this  respect.  Construct 
figures  for  the  dandelion  similar  to  those  of  the 
text  on  the  yarrow. 

c.  Fruit  and  seed.  Study  the  fruit  and  seed  of  the  dande- 
lion and  compare  them  with  the  fruit  and  seed  of 
the  yarrow. 

(1)  What  special  device  has  the  fruit  of  the  dandelion 

for  dispersal  ?  What  is  the  origin  of  the  parachute 
of  hairs  ?  To  what  part  of  the  flower  do  the 
hairs  correspond  ? 

(2)  Construct  a  series  of  three  figures  to  illustrate  the 

development  of  the  fruit  in  the  dandelion,  begin- 
ning with  closed  floral  heads  in  which  the  flowers 
have  been  recently  fertilized. 

3.  Seasonal  history.    Construct  figures  to  illustrate  the  sea- 

sonal history  of  the  dandelion.  Is  it  annual,  biennial, 
or  perennial  ?  By  what  means  does  it  spread  so  rapidly 
in  lawns  and  along  roadsides  ?  Study  the  relations  of 
its  leaves  to  the  grass  beneath  them.  State  five  reasons 
why  the  dandelion  is  so  successful  in  gaining  and 
holding  a  place  for  itself  in  lawns. 

4.  Analysis.    Ascertain  the  species  name  of  the  dandelion 

by  means  of  a  manual. 


SECTION  XII.    FIELD  WORK 
(MONOCOTYLEDONS) 

A.   TRADESCANTIA,  TULIP,  AND  OTHER  MONOCOTYLEDONS 

The  most  common  and  well-known  monocotyledons  include 
the  common  grasses,  sedges,  and  cereal  grains,  different  mem- 
bers of  the  lily  family,  palms,  bananas,  and  bamboos.  The 
student  should  consult  illustrated  manuals  and  texts  in  order 
to  form  a  general  idea  of  the  habitat  and  habit  of  the  mono- 
cotyledons. Examine  also  a  number  of  species  in  the  field  and 
in  the  laboratory,  as  outlined  below,  in  order  to  fix  the  main 
distinctive  characteristics  of  monocotyledons.  Tradescantia  and 
the  tulip  may  be  taken  as  types  for  special  examination. 

1.  Habitat.    How   many  of  the  above-mentioned   common 

monocotyledons  are  widespread  or  cosmopolitan  in 
habitat  ?  How  many  are  restricted  in  habitat  ?  Are 
most  of  these  monocotyledons  mesophytic,  xerophytic, 
or  hydrophytic  in  habitat  and  habit  ?  Can  you  name 
common  monocotyledons  belonging  to  all  three  of 
the  above  habitats  ?  Summarize  the  above  facts  in 
your  notes. 

2.  Habit.    Compare  monocotyledons  with  dicotyledons  in  the 

following  particulars  of  general  habit  and  structure : 
n.  Lc<i/'/'x. 

( I )  Form  and  venation.  What  are  the  distinctive  features 
of  the  leaves  of  monocotyledons  in  these  respects  ? 
Note  particularly  whether  monocotyledons  have 
open  or  closed  marginal  venation. 


186         LABORATORY  AND  FIELD  EXERCISES 

(2)  Study   and   draw   leaves    of   one   or   more    mono- 
cotyledons to  illustrate  the  form  and  mode  of 
venation  characteristic  of  the  group. 
b.  Stem. 

(1)  Aerial  and  underground  stems.    Do  monocotyledons 

generally  have  aerial  stems  as  well  developed  as 
dicotyledons  ?  How  is  this  in  grasses  and  cereals, 
cultivated  lilies,  narcissus,  tulips,  onions,  iris, 
palm?  Do  they  have  rhizomes,  bulbs,  and  tubers? 
Study  specimens  and  manuals  to  determine  this 
point.  Are  the  aerial  stems  of  monocotyledons 
mostly  flower-bearing  stems  or  are  they  well- 
developed  leafy  stems  ?  Are  monocotyledons 
mostly  herbs,  trees,  or  shrubs  ?  Compare  with 
dicotyledons  in  this  respect. 

(2)  Study  and  draw  the  underground  and  aerial  stem  or 

stems  of  one  or  more  monocotyledons.  Indicate 
nodes,  internodes,  buds,  and  annual  increments 
of  growth. 

(3)  Anatomy.    Cut  transverse  sections  of  the  aerial  stem 

of  some  monocotyledon  and  observe  the  sections 
with  low  and  high  powers  of  the  microscope. 
Are  there  the  usual  tissue  areas  characteristic 
of  the  stems  of  dicotyledons ;  namely,  epidermis, 
cortex,  and  the  vascular  ring  of  phloem,  xylem, 
and  pith  ?  Is  there  a  cambium  present  ?  How 
do  monocotyledon  stems  increase  in  thickness  ? 
Draw  your  section  in  outline,  naming  the  tissue 
layers  and  tissue  groups  as  you  think  they 
should  be  labeled.  Draw  a  single  vascular  bun- 
dle and  label  its  skeletal  and  conducting  tissues. 
Summarize  the  distinctive  features  of  the  anatomy 
of  monocotyledons  as  for  dicotyledons  above.  See 


THE  SPRING  FLORA  187 

the  discussion  of  the  stem  structure  of  mono- 
cotyledons in  Part  I  of  the  text. 
3.  Reproduction. 

a.  The  flower.     Study   the   structure   and  floral   plan   of 

flowers  of  one  or  more  monocotyledons. 

(1)  In  what  respects  are  these  flowers  like  the  flowers 

of  dicotyledons  already  studied  ?  In  what  respects, 
if  any,  are  they  different?  Have  the  flowers  of 
monocotyledons  and 'dicotyledons  the  same  num- 
ber of  floral  members  in  a  cycle  ?  See  your  speci- 
mens and  illustrated  manuals. 

(2)  Essential  organs  of  the  flower.    Compare  the  stamens 

with  those  of  dicotyledons.  Study  the  pistil  of  the 
tulip  or  of  a  similar  monocotyledon.  Cut  transverse 
sections  and  observe  the  relation  of  megasporo- 
phylls  or  carpels  which  enter  into  the  formation 
of  a  pistil  in  monocotyledons.  Is  the  placenta 
central  or  parietal  ?  Note  the  form  and  attach- 
ments of  the  ovules.  Draw  the  section  of  the 
pistil  and  ovules  greatly  enlarged.  Label. 

(3)  Ground  plan.    Construct  a  ground  plan  of  a  flower 

of  a  monocotyledon  and  compare  it  with  the 
similar  plan  made  of  the  flower  of  a  dicotyledon. 
In  what  fundamental  respect  are  the  two  different  ? 
In  what  respects  are  they  alike  ? 

b.  Seeds  and  embryo.    If  available,  study  the  seeds  and 

embryos  of  typical  monocotyledons,  including  a 
cereal,  such  as  corn  or  wheat.  In  what  respects 
do  the  seeds  and  embryos  of  typical  monocoty- 
ledons differ  from  those  of  dicotyledons  ?  Con- 
struct a  drawing  of  a  seed  of  a  monocotyledon  to 
show  the  relations  of  the  embryo,  endosperm,  and 
seed  coats. 


188          LABORATORY  AND  FIELD  EXERCISES 

4.  Summary  and  comparisons.  Summarize  the  contrasting 
characteristics  of  monocotyledons  and  dicotyledons 
under  the  following  headings : 

a.  Habit. 

(1)  Leaves :  form  and  venation. 

(2)  Stem :  general  characters  and  anatomy. 

(3)  Roots:  general  characters. 

b.  Reproduction. 

(1)  Floral  plan. 

(2)  Seed  and  embryo. 

Consult  the  text  discussion  under  the  comparison  of  dicoty- 
ledons and  monocotyledons. 

B.  SOLOMON'S  SEAL  (POLYGONATUM)  OR  FALSE  SOLOMON'S 
SEAL  (SMILACINA) 

1.  Habitat.    Ascertain  by  field  studies  the  natural  habitat 

of  such  forms  of  monocotyledons  as  the  Solomon's 
seal,  in  which  there  is  a  rhizome  and  an  aerial  stem. 
Are  they  typical  mesophytes  or  are  they  tropophytes 
(plants  which  adjust  themselves  alternately  to  typical 
mesophytic  conditions  and  to  dry  semixerophytic  condi- 
tions) ?  What  structural  provisions  have  the  true  and 
false  Solomon's  seal  for  such  environmental  adjustment? 
Is  this  a  common  adjustment  in  monocotyledons  with 
stems  in  the  form  of  rhizomes  or  bulbs  ? 

2.  Habit. 

a.  Tlie  rhizome,  or  underground  stem. 

(1)  Are  there  nodes  and  internodes  ?  leaf  scars  and  bud- 

scale  scars  ?  scars  produced  by  previous  aerial 
stems  ?  Are  there  other  evidences  that  the  rhi- 
zome is  a  stem  ? 

(2)  Buds  and  growth.  What  structures  are  produced 

each  season  by  the  growth  of  buds  on  the  rhizome  ? 


THE  SPRING  FLORA  189 

How  many  years  of  growth  are  represented  in 
your  specimen  ?  Is  the  aerial  stem  a  product  of  a 
terminal  or  of  a  lateral  bud  ?  How  is  the  growth 
of  the  stern  continued  after  the  production  of  the 
annual  aerial  stem  ?  Does  the  rhizome  branch 
underground  ? 

b.  Aerial  stem.  Compare  the  general  form  and  structure 

of  the  aerial  stem  and  rhizome.  Are  there  nodes, 
internodes,  buds,  and  branches  ? 

c.  Leaves.  Study  the  leaves  and  their  venation.    Compare 

their  form  and  venation  with  that  described  in 
the  text. 

(7.  Drawing.  Construct  a  drawing  to  illustrate  the  main 
structural  features  mentioned  above. 

3.  Anatomy.  Cut  transverse  sections  of  the  underground  and 

aerial  stems  and  stain  with,  iodine. 

a.  Compare  the  two  sections  as  regards  the  disposition  of 

the  skeletal,  storage,  and  vascular  systems.  What  is 
the  main  function  of  the  rhizome  ?  of  the  aerial  stem  ? 
Is  the  structure  of  each  stem  adapted  for  its  work  ? 

b.  Construct  outline  sketches  of  each  stem  to  illustrate 

the  distribution  of  the  three  classes  of  tissues  men- 
tioned above. 

4.  Reproduction. 

a.  Inflorescence.  Are  the  flowers  solitary  or  do  they  form 

•  an  inflorescence  ?  If  an  inflorescence  is  present,  to 
what  class  does  it  belong  ? 

b.  Flowers. 

(1)  Structure  and  floral  plan.  Compare  the  structure 
and  floral  plan  of  the  flower  that  you  are  studying 
with  that  of  a  typical  monocotyledon,  like  Trades- 
cantia,  described  in  the  text.  Is  the  flower  perfect, 
complete,  and  regular? 


190         LABORATORY  AND  FIELD  EXERCISES 

(2)  Pollination  features.  Ascertain  whether  the  flowers 

are  self-pollinating,  close-pollinating,  or  cross- 
pollinating.  Are  there  special  devices  for  securing 
pollination  ? 

(3)  Drawings.  Construct  a  ground  plan  of  the  flower 

and  outline  drawings  of  the  flowers  in  long  sec- 
tion to  illustrate  the  relation  of  anthers  and 
stigma  at  the  time  of  pollination. 

c.  Fruit  and  seed.    To  what  class  does  the  fruit  belong  ? 
Are  there  special  devices  for  seed  dissemination  ? 

5.  Seasonal  life.    Is  the  plant  you  are  studying  an  annual,  a 

biennial,  or  a  perennial  ?  What  are  the  seasonal  func- 
tions of  the  aerial  stem  and  rhizome  ?  Construct  a  series 
of  figures  to  illustrate  the  seasonal  life  of  Polygonatum 
or  Smilacina. 

6.  Analysis.  By  means  of  a  manual  ascertain  the  scientific 

name  of  the  species  studied. 


C.  IRIDACEAE  AND  ARACEAE 

1.  Habitat  and  habit.    Study  one  species  of  Iris  and  one  of 

Arum,  using  the  same  general  plan  as  that  outlined 
above  for  Polygonatum  and  Smilacina.  Be  able  to 
explain  the  seasonal  life  and  environmental  relations 
of  each. 

2.  Reproduction.    Consult  the  text  explanations  and  discus- 

sion of  Iris  and  jack-iu-the-pulpit. 

a.  Floral  plan.  Determine  the  floral  plan  in  each  case. 

b.  Structure.  Are  the  flowers  hypogynous,  perigynous,  or 

epigynous  ?  Are  they  complete,  perfect,  and  regular  ? 
Distinguish  between  the  parts  of  the  perianth.  Do 
you  find  stamens  and  pistil  of  the  regular  type 
characteristic  of  monocotyledons  ? 


THE  SPRING  FLORA  191 

c.  Pollination  in  Iris.  Consult  the  text  description  and 

confirm  the  structural  arrangements  there  explained 
concerning  the  pollinating  mechanism  in  Iris. 

d.  Pollination  in  jack-in-tlic-pulpit.  Be  able  to  explain  the 

special  devices  for  pollination  in  jack-in-the-pulpit. 

3.  Summary.  Summarize  the  method  and  the  special  mechan- 

isms for  securing  cross-pollination  in  Iris  and  jack-in- 
the-pulpit. 

4.  Seasonal  history.    Be  able  to  explain  and  illustrate  the 

seasonal  history  of  Iris  and  jack-in-the-pulpit. 

D.  GRAMINEAE 

1.  Habitat  and  habit.    Follow  the  plan  outlined  above  in 

the  general  directions  for  studying  monocotyledons. 

2.  Reproduction.    Study  the  reproductive  structures  of   the 

common  cultivated  oat  (Avena),  using  the  text  discus- 
sion and  figures  to  assist  you  in  understanding  the 
inflorescence,  flower,  and  fruit.  Make  appropriate  draw- 
ings of  inflorescence  and  flowers. 

3.  Seasonal  history.    Be  able  to  illustrate  the  seasonal  his- 

tory of  some  common  grass  and  explain  the  seasonal 
functions  of  its  main  organs. 

4.  Economic  importance.  Summarize  the  facts  relating  to  the 

economic  importance  of  the  plants  belonging  to  the 
grasses  and  the  grass  family  (G-ramineae). 


SECTION  XIII.   PLANT  ASSOCIATIONS 

In  a  preliminary  course  in  botany  very  little  time  is  avail- 
able for  the  study  of  ecology.  A  brief  field  study  will,  how- 
ever, give  the  student  a  valuable  insight  into  the  social  life 
of  plants  and  their  dynamic  relation  to  the  environment.  The 
following  studies  may  well  be  assigned  early  in  the  spring  term 
and  followed  as  the  season  advances : 

1.  Nature  and  composition  of  plant  associations.  Make  a 
preliminary  study  of  any  area  of  soil  ten  or  fifteen  feet 
square  covered  with  vegetation,  as  indicated  in  the 
following  outline: 

a.  Kind    and    number  of  species   associated  together   in 

one  area. 

(1)  Count   the   number  of  different   kinds    of   plants 

inhabiting  the  area  under  observation.  Name 
as  many  of  the  species  as  possible  and  determine 
unknown  species  by  consulting  manuals. 

(2)  Make  the  same  determination  for  a  similar  area 

somewhat  removed  from  the  first  in  the  same 
plant  association.  Do  you  find  any  consider- 
able variation  in  the  two  portions  of  the  same 
association  ?  If  so,  account  for  the  variation  in 
number  and  kind  of  species  occupying  the  two 
areas. 

b.  Habitat  and  habit  of  associated  plants. 

(1)  Determine  as  far  as   possible  the  environmental 
factors   which    characterize    the    habitat    under 
observation   and   their  effect   on   plant   growth. 
192 


THE  SPRING  FLORA.  193 

The  principal  factors  to  be  considered  are  sun- 
shine, shade,  relative  humidity,  temperature,  and 
soil  conditions.  Determine  also  the  nature  of  the 
soil  as  far  as  possible,  taking  into  account  the 
water  content,  amount  of  humus,  acidity,  mineral 
salts,  etc. 

c.  Structure  and  seasonal  life  of  associated  plants. 

(1)  Are  the  plants  inhabiting  the  area  under  considera- 

tion mesophytes,  xerophytes,  or  hydrophytes?  Are 
they  annuals,  biennials,  or  perennials  in  habit  ? 
Have  they  any  special  adaptations  which  fit  them 
for  life  in  the  habitat  under  observation  ? 

(2)  What  are  the  dominant  species  ?  Can  you  determine 

why  they  are  dominant?  Is  their  dominance  due 
to  structural  adaptations  of  leaf,  stem,  or  root  ? 
Is  dominance  due  to  vegetative  or  other  means 
of  rapid  propagation  and  dissemination  ?  Is  it 
due  in  any  measure  to  a  perennial  or  biennial 
seasonal  life? 

d.  Summary. 

(1)  Draw  a  chart  to  indicate  the  distribution  and  abun- 

dance of  the  three  or  four  dominant  species  of  the 
area  examined.  This  may  be  done  by  using  circles, 
squares,  and  triangles  of  different  sizes  to  repre- 
sent different  species,  or  by  using  the  initial  letter 
of  each  species  to  represent  the  position  of  the 
species  in  the  plotted  area  (see  Fig.  288  of  text). 

(2)  List  the  species  found,  indicating  whether  they  are 

annuals,  biennials,  or  perennials.  Indicate  also 
whether  they  are  mesophytic,  xerophytic,  or 
hydrophytic  in  habit. 

(3)  Work  out  by  means  of  outline  diagrams  the  seasonal 

history  of  one  or  two  dominant  species  of  the  habitat. 


194         LABORATORY  AND  FIELD  EXERCISES 

(4)  Define  a  plant  association.  "What  are  the  most 
important  considerations  which  determine  the 
kind  of  dominant  species  composing  the  associa- 
tion you  have  just  studied  ? 

2.  Kinds  of  associations.    Study  the  vegetation  on  the  margin 

of  a  pond,  lake,  or  stream,  including  the  aquatic  plants, 
the  plants  of  the  shore,  and  those  of  the  drier  regions 
adjoining  the  shore. 

a.  Zonotion,    Do  you  note  any  regularity  in  the  arrange- 

ment of  definite  types  of  plants  in  the  water  and 
along  the  shore  ?  Are  there  definite  associations  of 
plants  thus  arranged?  Is  the  arrangement  suffi- 
ciently regular  to  constitute  definite  zones  of  vege- 
tation ?  See  the  text  and  figures  illustrating  the 
nature  of  zonation. 

b.  Kind  and  number  of  species  in  each  zone  or  association. 

(1)  What  plants  grow  in  the  water  ?  Are  there  floating 

and  attached  algae  or  seed  plants  ?  What  plants 
grow  along  the  immediate  shore  line  ?  Study  the 
species  in  each  zonelike  association.  Do  you 
find  any  discrepancy  between  the  habitat  and 
the  habit  of  plants  in  any  given  association  ? 
If  so,  explain. 

(2)  Determine  the  nature  of  the  habitat  and  the  environ- 

mental factors  controlling  the  association  of  plants 
in  each  zone  of  vegetation  under  consideration. 
Observe  the  structural  adaptations  of  the  species 
in  the  various  zones. 

3.  Summary  and  conclusions. 

a.  Draw  an  outline  diagram  of  the  shore  line  investigated 
and  indicate  by  symbols  (such  as  circles,  squares,  tri- 
angles, crosses,  etc.)  the  different  zones  of  vegetation 
and  the  number  and  kinds  of  plant  associations  found. 


THE  SPRING  FLORA  195 

b.  List  the  dominant  species  of  each  association  and  indi- 

cate whether  they  are  annuals,  perennials,  biennials, 
rnesophytes,  xerophytes,  or  hydrophytes. 

c.  Discuss  the  relation  of  the  habitat  of  each  association 

observed  to  the  habit  of  the  species  comprising  the 
association. 

d.  Explain  any  discrepancy  found  between  the  habitat  and 

the  habit  of  plants  in  the  shore  associations  studied. 
4.  Origin  of  new  associations. 

a.  Shore-line  associations.   Do  you  find  indications  of  migra- 

tion, invasion,  and  succession  in  the  shore-line  associa- 
tions ?  Are  plants  invading  the  mud  or  gravel  of  the 
immediate  shore  zone  ?  If  so,  what  kinds  of  plants 
are  they,  and  from  what  place  did  they  come  ?  Are 
they  species  with  special  devices  for  dissemination  ? 
Are  they  found  in  the  adjacent  associations  or  are 
they  migrants  from  distant  locations  ?  Have  they 
any  special  adaptations  for  their  new  habitat  ?  Do 
you  see  any  evidence  of  succession,  or  the  replace- 
ment of  one  association  by  another  ?  Discuss  in  your 
notes  the  phenomena  observed. 

b.  Denuded  areas.  Select  an  area  from  which  the  vegetation 

has  been  removed  within  a  comparatively  short  period, 
as  on  a  denuded  bank,  field,  garden,  or  roadside. 

(1)  What  plants  are  invading  the  area  ?  Are  they  from 

the  adjacent  vegetation  ?  "What  are  the  means 
by  which  these  species  originally  migrated  to  the 
new  home  ?  Have  they  special  adaptations  for 
becoming  established  in  the  new  habitat?  Is 
there  a  definite  relation  between  the  habitat  and 
the  habit  of  the  invading  species  ? 

(2)  Discuss  the  above  facts  concerning  the  area  being 

investigated. 


INDEX 


(References  to  illustrations  are  indicated  by  asterisks  accompanying  page  numbers 


Achiliea  (yarrow),  181 

Adjustment  to  environment,  19 

Algse,  75  ;  general  study  of,  82 

American  elm,  plan  and  develop- 
ment, 13,  110* 

Anaphase,  37 

Anatomy,  of  Adiantum,  116 ;  of 
Pteris  aquilina,  118 

Angiosperms  (dicotyledons),  143 ; 
sporophyte  of,  143  ;  reproduction 
of,  146  ;  hardwood  trees,  161 

Anthers,  65 

Apple,  cultivated,  180 

Araceae,  190 

Aspergillus,  96 

Aster,  9 

Bacteria,  89,  91* 

Bark,  41,  42  ;  kinds  of,  164* 

Body  plan,  3  ;  of  lilac,  3  ;  spiral,  4* 

Bryophyta,  103 

Buds,  section  of,  5* ;  structure  and 

growth  of,  34 
Buttercup,  171 

Capsella,   ovule   and  embryo,    67* ; 

flower  of,  149 
Catnip,  9 
Cell,  and  tissue  differentiation,  23* ; 

and  cell  division,  35 
Cell  division  (mitosis),  35 
Cell  structure  and  growth,  31 
Cells,  growth  of,  33* 
Cellular  structure,  22 
Cell-wall  thickening,  24* 
Chlamydomonas,  76 
Chloroplastids  in  Elodea,  30 
Chromoplastids,  31 
Chromosomes,  35 
Cinquefoil  (Potentilla),  179 
Collenchyma,  24* 
Columbine  (Afjuiliyiti).  173 


Compositae,  181 
Coniferales,  135 
Cross-pollination,  70 
Cruciferae,  17 5 
Cycadales  (cycads),  130 
Cyclic  plan  of  milkweed,  6* 

Dandelion,  183 

Dicotyledons     (angiosperms),     143 ; 

stems  of,  50,  51*  ;  trees  and  shrubs, 

155  ;  herbaceous,  167 

Ecological  relations  of  plants,  63 

Elm,  American,  13,  16* 

Elodea  canadensis,  30 

Equisetales,  123  ;  sporophyte  of,  123 

Equisetum  arvense,  125  ;  life  history 
of,  126 

Experiments,  on  tropisms,  20  ;  fer- 
mentation, 88 ;  on  bacteria,  89 

False  Solomon's  seal,  188 

Family  record,  trees,  157  ;  herbs,  170 

Fermentation  experiments,  88 

Filicales,  113;  sporophyte,  113;  asex- 
ual reproduction,  120 ;  gameto- 
phyte,  121  ;  life  history  of,  122 

Flower,  parts  of,  64  ;  of  angiosperms, 
146,  147* 

Frtii/ftrift  (stra\vberry),  179 

Fucus  vesiculosus,  83 

Fungi,  86 

Gramineae,  191 

Growth,  of  root  tips,  31  ;  of  root-tip 

cells,  33* 
Gymnosperms,  130  ;  softwood  trees, 

159 

Hawthorn,  bud  of,  5* 

H<  l/init/iii.^  tmnuus,  stem  sections,  51* 
Hepatica,  171 


197 


198         LABORATORY  AND  FIELD  EXERCISES 


Ilcpaticae,  103 

Herbaceous  dicotyledons,  107 

Herbaceous  plants,  plan  of,  (i*  ;  body 

plan  of,  6  ;  buds  of,  7 
Herbaceous  steins,  dicotyledons,  50  ; 

monocotyledons,  52 

Income  and  outgo,  8* 
Iridaceae,  100 
7m,  100 

Jack-in-the-pulpit,  100 

Leaf,  structure  of,  53,  54*,  55*  ;  veins 

of,  55* 

Leguminosae,  177 
Lichens,  101 
Lilac,  3 

Lilac  mildew,  102 
Lily,  flower  of,  147* 
Liverworts,  103,  105*,  106* 
Lycopodiales,  126 
Lycopodium,  126 

Marchantia,  105*,  106* 

Metaphase,  36 

Microsphaera  aini,  102 

Milkweed,  cyclic  plan  of,  6* 

Mitosis,  35 

Mold,  Khizopuu,  94  ;  PenicWium,  96  ; 

Asperyillus,  96 
Molds,  general  nature  of,  92 
Monocotyledons,  52 ;    structure  of, 

52  ;  field  work,  185 
Morning-glory,  seed  and  seedling  of, 

19* 

Motor  organs,  19 
Musci  (mosses),  108 
Mushrooms,  97 

Nutrition  and  seasonal  life,  61 

CEdogonium,  81 
Ovule  of  Capsdla,  67* 

Papilionaceous  flowers,  pollination 
of,  68 ;  structure  of,  69 ;  cross- 
pollination,  70 

Penicillium,  96 

Photosynthesis,  57 
Physiology,  experiments  in,  57 


Pine,  white,  10*  ;  study  of,  159 

Pines,  form  of,  9 

Pistil,  05 

Plant  associations,  192 

Plastids,  30 

Pollination,  68.  See  also  Cross- 
pollination 

Polijgonutum  (Solomon's  seal),  188 

Poplar,  vegetative  and  reproductive 
parts  of,  157 

Potentilla  (cinquefoil),  179 

Prophase,  35 

Protococcus,  75 

Pteridophyta,  113 

Pteris  aquilina,  anatomy  of,  118 

Puffballs,  99 

Pulvini,  19 

Ragweed,  9 

Ranunculaceae    (buttercup    family), 

171 ;  floral  modifications  of,  173 
Reproduction,  64 
Respiration,  60 
Rhizopus,  94 
Ricciocarpus,  107 
Roots,  structure  of,  53 
Root-tip  cells,  26 
179 


Seasonal  life  and  nutrition,  61 
Seed  and  seedlings,  morning-glory, 

19* 

Selcginella,  127  ;  sporophyte  of,  127 
Selaginella  martensii,  128* 
Shepherd's  purse,  149 
Smilacina    (false    Solomon's    seal), 

188 

Smuts,  100 

Solomon's  seal  (Poli/gonalitm),  188 
Species   record,   trees,   156 ;    herbs, 

168 

Spindle,  36 
Spirogyra,  11 
Spruce,  anatomy  of,  136;    asexual 

reproduction    of,     139 ;    gameto- 

phyte  of,  141 
Spruce  and  pine,   135;  sporophyte, 

135 

Spruces,  form  of,  9 
Stamen  hairs  of  Tradescantia,  27 
Strawberry,  179 


INDEX  199 

Telophase,  37  Water  ascent,  62,  71 

Thallophytes,  75  Wheat,  kernel  and  section  of,  66* 

Tradescaidia,  stamen  hairs  of,  27  Woody  stems,  anatomy.  41  ;  micro- 
Transpiration,  01  scopic  structure,  45 

Tree,  structure  and  growth  of,  44*  Wound,  healing  of,  46* 
Trees,   spruces  and  pines,  9;     and 

shrubs,  155  Yarrow  (Achillea),  181 

Yeast,  86,  87* 
Vegetable  fibers,  25* 

Violaceae,  173  Zamia,  gametophyte  of,  133 


SOUTHERN  BRANCH, 

UNIVERSITY  OF  CALIFORNIA, 

LIBRARY, 

ANGELES.  CALIF. 


